THERMOCHEMISTRYSections 171 172

ENERGY CHANGES

The amount of energy a substance has is determined by the arrangement of atoms Aka ndash the bonds amp their location in the molecule

In a CAR

Gasoline (hydrocarbon) has high chemical potential energy (a lot of energy stored in amp between bonds) Controlled explosions cause the gasoline to release

energy This energy does work to make it run This also makes the engine HOT

Energy changes occur either as _____________________________________________

HEAT (VARIABLE Q) Always flows from a __________object to a

_____________object Until both temperatures are the same (equilibrium)

___________ndash what yoursquore focused on ________________ndash everything else Law of conservation of energy

If energy of system increases energy in surroundings must decrease vice versa

____________________ reaction System gains heat as surroundings cool down

You (the system) sitting near a fire (surroundings) Heat flowing into a system = ______________

____________________reaction System loses heat as surroundings absorb it amp heat up

You (the system) running and releasing heat into the surrounding (whatrsquos around you)

Heat flowing out of the system = ______________

UNITS

Common = calorie and joule (SI unit) 1 Calorie (food) = 1 kilocalorie = 1000 calories

(notice the capital C in the 1st one) 1 calorie (cal) = 4184 Joules (J) Sohellipa snickers bar (250 Calories) = 250000

calories = 59751 J of energy To put this in perspective (very rough calculations)

A 200lb man walking 1 mile in 31 minutes (slowhellip) uses 13583 joules of energyhelliphelliphelliphelliphmmhellipversus what you take in from a Snickers

1 calorie is defined as _____________________________________________________________________

_______________________________________________

HEAT CAPACITY

The amount of heat required to raise the temp of an object exactly 1degC

Heat capacity depends on both the mass and chemical composition of the substance (extensive property) Greater mass = greater heat capacity

(larger pots of water take longer to boil)

Specific heat capacity (specific heat C ) _____________________________________________

_____________________________________________________________________________________________

(intensive property)

HEAT CAPACITY CALCULATIONS

Heat = mass x specific heat x change in temperature in Celsius

q = Units for specific heat= J(gdegC) OR cal(gdegC)

Practice When 435 J of heat is added to 34 g olive oil at 21degC the temperature increases to 85 degC What is Colive oil

C=qm ΔT = 435 J (34g x (85-21degC)) Colive oil = 1999 = 20 J(gdegC)

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

ENERGY CHANGES

The amount of energy a substance has is determined by the arrangement of atoms Aka ndash the bonds amp their location in the molecule

In a CAR

Gasoline (hydrocarbon) has high chemical potential energy (a lot of energy stored in amp between bonds) Controlled explosions cause the gasoline to release

energy This energy does work to make it run This also makes the engine HOT

Energy changes occur either as _____________________________________________

HEAT (VARIABLE Q) Always flows from a __________object to a

_____________object Until both temperatures are the same (equilibrium)

___________ndash what yoursquore focused on ________________ndash everything else Law of conservation of energy

If energy of system increases energy in surroundings must decrease vice versa

____________________ reaction System gains heat as surroundings cool down

You (the system) sitting near a fire (surroundings) Heat flowing into a system = ______________

____________________reaction System loses heat as surroundings absorb it amp heat up

You (the system) running and releasing heat into the surrounding (whatrsquos around you)

Heat flowing out of the system = ______________

UNITS

Common = calorie and joule (SI unit) 1 Calorie (food) = 1 kilocalorie = 1000 calories

(notice the capital C in the 1st one) 1 calorie (cal) = 4184 Joules (J) Sohellipa snickers bar (250 Calories) = 250000

calories = 59751 J of energy To put this in perspective (very rough calculations)

A 200lb man walking 1 mile in 31 minutes (slowhellip) uses 13583 joules of energyhelliphelliphelliphelliphmmhellipversus what you take in from a Snickers

1 calorie is defined as _____________________________________________________________________

_______________________________________________

HEAT CAPACITY

The amount of heat required to raise the temp of an object exactly 1degC

Heat capacity depends on both the mass and chemical composition of the substance (extensive property) Greater mass = greater heat capacity

(larger pots of water take longer to boil)

Specific heat capacity (specific heat C ) _____________________________________________

_____________________________________________________________________________________________

(intensive property)

HEAT CAPACITY CALCULATIONS

Heat = mass x specific heat x change in temperature in Celsius

q = Units for specific heat= J(gdegC) OR cal(gdegC)

Practice When 435 J of heat is added to 34 g olive oil at 21degC the temperature increases to 85 degC What is Colive oil

C=qm ΔT = 435 J (34g x (85-21degC)) Colive oil = 1999 = 20 J(gdegC)

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HEAT (VARIABLE Q) Always flows from a __________object to a

_____________object Until both temperatures are the same (equilibrium)

___________ndash what yoursquore focused on ________________ndash everything else Law of conservation of energy

If energy of system increases energy in surroundings must decrease vice versa

____________________ reaction System gains heat as surroundings cool down

You (the system) sitting near a fire (surroundings) Heat flowing into a system = ______________

____________________reaction System loses heat as surroundings absorb it amp heat up

You (the system) running and releasing heat into the surrounding (whatrsquos around you)

Heat flowing out of the system = ______________

UNITS

Common = calorie and joule (SI unit) 1 Calorie (food) = 1 kilocalorie = 1000 calories

(notice the capital C in the 1st one) 1 calorie (cal) = 4184 Joules (J) Sohellipa snickers bar (250 Calories) = 250000

calories = 59751 J of energy To put this in perspective (very rough calculations)

A 200lb man walking 1 mile in 31 minutes (slowhellip) uses 13583 joules of energyhelliphelliphelliphelliphmmhellipversus what you take in from a Snickers

1 calorie is defined as _____________________________________________________________________

_______________________________________________

HEAT CAPACITY

The amount of heat required to raise the temp of an object exactly 1degC

Heat capacity depends on both the mass and chemical composition of the substance (extensive property) Greater mass = greater heat capacity

(larger pots of water take longer to boil)

Specific heat capacity (specific heat C ) _____________________________________________

_____________________________________________________________________________________________

(intensive property)

HEAT CAPACITY CALCULATIONS

Heat = mass x specific heat x change in temperature in Celsius

q = Units for specific heat= J(gdegC) OR cal(gdegC)

Practice When 435 J of heat is added to 34 g olive oil at 21degC the temperature increases to 85 degC What is Colive oil

C=qm ΔT = 435 J (34g x (85-21degC)) Colive oil = 1999 = 20 J(gdegC)

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

UNITS

Common = calorie and joule (SI unit) 1 Calorie (food) = 1 kilocalorie = 1000 calories

(notice the capital C in the 1st one) 1 calorie (cal) = 4184 Joules (J) Sohellipa snickers bar (250 Calories) = 250000

calories = 59751 J of energy To put this in perspective (very rough calculations)

A 200lb man walking 1 mile in 31 minutes (slowhellip) uses 13583 joules of energyhelliphelliphelliphelliphmmhellipversus what you take in from a Snickers

1 calorie is defined as _____________________________________________________________________

_______________________________________________

HEAT CAPACITY

The amount of heat required to raise the temp of an object exactly 1degC

Heat capacity depends on both the mass and chemical composition of the substance (extensive property) Greater mass = greater heat capacity

(larger pots of water take longer to boil)

Specific heat capacity (specific heat C ) _____________________________________________

_____________________________________________________________________________________________

(intensive property)

HEAT CAPACITY CALCULATIONS

Heat = mass x specific heat x change in temperature in Celsius

q = Units for specific heat= J(gdegC) OR cal(gdegC)

Practice When 435 J of heat is added to 34 g olive oil at 21degC the temperature increases to 85 degC What is Colive oil

C=qm ΔT = 435 J (34g x (85-21degC)) Colive oil = 1999 = 20 J(gdegC)

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HEAT CAPACITY

The amount of heat required to raise the temp of an object exactly 1degC

Heat capacity depends on both the mass and chemical composition of the substance (extensive property) Greater mass = greater heat capacity

(larger pots of water take longer to boil)

Specific heat capacity (specific heat C ) _____________________________________________

_____________________________________________________________________________________________

(intensive property)

HEAT CAPACITY CALCULATIONS

Heat = mass x specific heat x change in temperature in Celsius

q = Units for specific heat= J(gdegC) OR cal(gdegC)

Practice When 435 J of heat is added to 34 g olive oil at 21degC the temperature increases to 85 degC What is Colive oil

C=qm ΔT = 435 J (34g x (85-21degC)) Colive oil = 1999 = 20 J(gdegC)

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HEAT CAPACITY CALCULATIONS

Heat = mass x specific heat x change in temperature in Celsius

q = Units for specific heat= J(gdegC) OR cal(gdegC)

Practice When 435 J of heat is added to 34 g olive oil at 21degC the temperature increases to 85 degC What is Colive oil

C=qm ΔT = 435 J (34g x (85-21degC)) Colive oil = 1999 = 20 J(gdegC)

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

MORE HEAT CALCULATIONS

How much heat is required to raise the temperature of 2500 g of Hg by 52ordmC (CHg = 014 J(gordmC))

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

STOP

END OF 161

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

CALORIMETRY EEK Measures heat flow IN or OUT of a system Heat released by system = heat

absorbed by surroundings (equal in value but opposite in sign) In aq rxns system = chemicals surroundings =

water Good bc know Cwater and Dwater to calc mwater

Calorimeter (measures heat flow) Enthalpy (H) Δ = q at constant pressure

(which they will all be) ______________________ - ΔH =

+ ΔH =

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

CALORIMETRY CALCULATIONS Practice

When 500 mL of water containing 050 mol HCl at 225degC is mixed with 500 mL of water containing 050 mol of NaOH at 225 degC in a calorimeter the temperature of the solution increases to 260degC How much heat (in kJ) was released by this reaction

Water = surroundings rxn= system Mass water =

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

MORE CAL CALCULATIONS A small pebble is heated up and placed in

a foam cup calorimeter containing 250 mL of water at 250degC The water reaches a max temp of 264degC How many joules of heat were released by the pebbleSystem = pebble surroundings = water

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HEAT EXCHANGE

Theory behind heat exchange _________________

________________________

Suppose a piece of gold with a mass of 215 g at temperature of 9500 oC is dropped into an insulated calorimeter containing 1250 g of water at 2200 oC What will be the final temperature of the water

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

STOP amp PRACTICE

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

THERMOCHEMICAL EQUATIONS In a chemical equation the heat (enthalpy) change for the

reaction can be written as either a reactant (endothermic) or product (exothermic)

EX CaO (s) + H2O (l) Ca(OH)2(s) + 652 kJThis means 625 kJ is released during this rxn

AKA

CaO (s) + H2O (l) Ca(OH)2(s) ΔH = -652kJ

Thermochemical equation States MUST be listed since different ΔH

Ex H2O (l) requires 44 kJ more than H2O (g) to separate into constituent gases

Heat of reaction The amount of heat absorbed or released during a

reaction depends on the number of ____________ of reactants involved

ΔH given in kJ but understood to be kJmol (see above example)

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

FIGURE 177

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

THERMOCHEMICAL CALCULATIONS

When carbon disulfide is formed from its elements heat is absorbed Calculate the amount of heat (in kJ) absorbed when 566 g of carbon disulfide formed

C(s) + 2S(s) CS2(l) ΔH = 893 kJ

566g CS2 ndash turn it into moles and thenhellip

Does this make sense

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

MORE THERMOCHEMISTRY CALCULATIONS

The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction How many kilojoules of heat are produced when 340 mol Fe2O3 reacts with an excess of CO

Fe2O3 (s) + 3CO (g) 2Fe (s) + 3CO2 (g) +

263 kJ340 mol Fe2O3 x 263 kJmol

=

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HEAT IN CHANGES OF STATE

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

PHASE CHANGE CALCULATIONS

While heating (temp is changing) Use normal equation q=mcΔT

While changing state (temp is constant) q= ΔHfus or vap x (moles)

ΔHfus for water = 601kJmol ΔHvap for water = 407kJmol

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HOW MUCH TOTAL HEAT IS NEEDED TO CONVERT 1000 GRAMS OF -10degC ICE TO 120degC STEAM hellipPREPARE YOURSELVES

q= mciceΔT cice = 21 JgC

ΔHfus = 601 kJmol = 6010 Jmol

q= mcwaterΔTcwater = 4184 JgC

ΔHvap = 407 kJmol = 40700 Jmol

q= mcsteamΔT csteam = 17 JgC

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

PUT WORK HERE

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

MOLAR HEAT OF FORMATION

The enthalpy change occurring during a reaction can also be calculated using the molar heats of formation of the reactants and products

Table 174 on page 530 in your text bookhellip ΔH0 = ΔHf

0 (products) ndash ΔHf0 (reactants)

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

HESSrsquoS LAW OF HEAT SUMMATION

Hessrsquos law adds two or more ldquohalfrdquo reactions and coordinating changes in enthalpy (ΔH) to get finaltotal reaction ΔH

Ex Derive C(graphite) + 2H2 (g) CH4(g)

(1) H2(g) + 12 O2(g) H2O(l) ΔH = -2858 kJ

(2) C(graphite) + O2(g) CO2(g) ΔH = -2935 kJ

(3) CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ΔH = -8904 kJ

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW

ANSWER

C(graphite) + 2H2 (g) CH4(g) ΔH = -747 kJ HOW