FUNDAMENTAL CHEMICAL LAWS

1789 - Lavoisier Law of Conservation of Massin a chemical reaction mass is neither created nor destroyed.

1820 - Proust. Law of Definite ProportionsA given compound always contain exactly the same proportion of elements by weight.

1820 - Dalton. Law of Multiple ProportionsWhen two elements form multiple compounds, the ratios of elemental masses can always be reduced to small whole numbers.

1811 - Avogadro. Avogadro’s HypothesisAt the same temperature and pressure, equal volumes of different gases contain the same number of particles.

جرم پايستگي قانوناز- ونه آيد مي وجود به نه جرم شيميايي واكنش يك در

رود مي بينيا

-: شيميايي واكنش يك در

ها دهنده واكنش جرم فراورده =مجموع جرم مجموع ها

معين نسبتهاي قانون

A sample of a compound composed of only carbon and hydrogen contains 79.89% carbon. Show that this compound obey the law of multiple proportions.

A 5.00- g sample of calcium was burned, yielding 6.996 g of a calcium-oxygen compound. How many grams of oxygen was taken up in the reaction?

If 6.001 mg of a compound containing only carbon and hydrogen is burned completely in oxygen and yields 17.60 mg of carbon dioxide and 10.81 mg of water, how much oxygen is used up?

شيميايي واكنشماده-- يك حداقل آن در كه است فرايندي

. شود ايجاد شيميايي تغيير وسيله به جديد

ها دهنده :واكنشحضور-- واكنش شروع از قبل كه موادي) شوند.) مي نوشته چپ طرف در دارند

ها :فراوردهمي-- توليد شيميايي واكنش در كه موادي

) شوند.) مي نوشته راست طرف در شوند

CHEMICAL EQUATION

-- a written statement using symbols and formulas to describe a chemical reaction.

or , it is

-- Chemist’s shorthand like

algebra to mathematicians

recipes to a chef

acronyms to the military

commuter jargon

Format:

1. Reactants on left, before reaction occurs.

2. Products on right, after reaction occurs.

3. Arrow points to products and means:

“goes to”, “produces”, “forms”,

“reacts to give”

4. + sign used between different reactants and

products.

Requirements:

1. Must be consistent with experimental facts.

2. Obeys conservation of mass.

Information conveyed by the Balanced Equation for the combustion of methane

ها دهنده ها واكنش فراورده

CH4)g( + 2O2)g( CO2 )g( + 2H2O)g(

CO2 مولكول CH4 1 مولكول 1

O2 مولكول 2 + H2O مولكول 2 +

1 mol CH4 1 mol CO2

+ 2 mol O2 + 2 mol H2O

6.022 x 1023 CH4 مولكول 6.022 x 1023 CO2 مولكول+ 2)6.022 x 1023 ( O2 مولكول +2 )6.022 10x 23 ) H2 O مولكول

16 g CH4 + 2)32 g(O2 44 g CO2 + 2)18 g( H2O

80 g ها دهنده ها 80 g واكنش فراورده

در استفاده مورد هاي نمادشيميايي واكنشهاي

نماد معنا

” ” “ كند مي توليد يا دهد “مي” شود مي “تشكيل

+ “ “ “ “ واكنش يا و يا عالوه بهبا دهد ”“مي

)s( جامد )l( مايع )g( گاز )aq( آبي محلول

شيميايي هاي واكنش انواع

اكسايش حالت در تغيير بدون ويا اكسايش حالت در تغيير با) احتراق) سوختن

CH4)g( + 2O2)g( CO2 )g( + 2H2O)g() تركيب) سنتز

A + X AXFe)s( + S)s( FeS)s(

تجزيهAX A + X2NaHCO3)s( Na2CO3 )s( + H2CO3 )g(

) ( يگانه جايگزيني يگانه جابجاييA + BX B + AX

or Y + BX BY + XFe)s( + CuSO )aq( Cu)s( + FeSO4)aq(

دوگانه جابجاييAX + BY AY + BX

رسوبي واكنشهايگاز تشكيل واكنشهاي

هيدروليز) ( باز و اسيد شدن خنثي واكنشهايNaOH)aq( + HCl)aq( NaCl)aq( + H2O)l(

DECOMPOSITION REACTIONSمي تجزيه مربوطه هاي عنصر به نوبل فلزهاي اكسيدهاي

.شوند

2 Au2O3(s) 4Au(s) + 3O2 (g)

هاي هاليدPtCl4(s) Pt(s) + 2Cl2 (g)

Peroxides decompose to oxides and oxygen gas

2H2O2(aq) 2H2O(l) + O2 (g)

Metal carbonates decompose to metal oxides and carbon dioxide gas; however, Group IA(I) metal carbonates do not decompose.

NiCO3(s) NiO(s) + CO2(g)

Metal nitrates decompose to metal nitrites and oxygen gas if the metal is Al, and alkali metal, or an alkaline-earth metal; other metal nitrates decompose to metal oxides, nitrogen dioxide gas, and oxygen gas

2KNO3(s) 2KNO2(s) + O2(g)

2Zn(NO3)2(s) 2ZnO(s) + 4NO2(g) + O2 (g)

Oxoacids decompose to nonmetal oxides and water

H2SO3(aq) SO2 (g) + H2O(l)

(Au, Pt, Hg)

DECOMPOSITION REACTIONS

Oxoanion salts containing hydrogen ions decompose to oxoanion salts and oxoacids; the oxoacids may decompose further.

2NaHCO3(s) Na2CO3 (s) + H2O(g) + CO2 (g)Metal hydroxides decompose to metal oxides and water

Ca(OH)2(g) CaO(s) + H2O(g)Hydrates lose water to form an anhydrous salt.

CuSO4.5H2O(s) CuSO4(s) + 5H2O(g)Ammonium salts lose ammonia; if the salt contains an anion that is a strong oxidizing agent (such as nitrate, nitrite, or dichromate), oxidation-reduction produces an oxide, water, and nitrogen gas.

(NH4)2SO4(s) 2NH3 (g) + H2SO4(l)

(NH4) 2Cr2O7(s) Cr2O3(s) + 4H2O(g) + N2(g)

BALANCING CHEMICAL EQUAITONS

A Balanced equation has an equal number of each element in reactants as in products.

Coefficients -- number of moles of a substanceSubscripts -- number of atoms of an element or

polyatomic ions in one mole of the substance )compound(coefficient – multiplier for H and O

2 H2Osubscript – multiplier for H onlycoefficient – multiplier for Ca, P and O

3 Ca3)PO4(2

subscripts – 3 multiplier for Ca - 4 multiplier for O - 2 multiplier for both P & O

STEPS TO BALANCE AN EQUATION

1. Coefficients are the smallest set of whole numbers.

2. Consider polyatomic ions as single entities (use () to keep them together).

3. Subscripts in a compound may not be changed during balancing, only coefficients may be.

4. Product compounds of a reaction will be given or predicted from known principles.

5. Balancing “by inspection” is the method for this class. Certain reactions which involve changes in oxidation states require more detailed methods.

6. All chemical equations are the result of experimental data and may be verified by experiment.

Classify each of the following equations as balanced or unbalanced.

a. TiCl4 + 2Ti 2TiCl3

b. SO2 + H2O H2SO3

c. 4NH3 + 3O2 2N2 + 6H2O

d. CS2 + 2O2 CO2 + 2SO2

Balance the following equations.

• N2 + O2 NO

• SO2 + O2 SO3

• U + F2 UF6

• Al + O2 Al2O3

• H2O H2 + O2

• Li + N2 Li3N

• Al + N2 AlN

• H2O + O2 H2O2

• C2H4 + O2 CO2 + H2O

• C3H6 + O2 CO2 + H2O

• C4H8 + O2 CO2 + H2O

• C5H10 + O2 CO2 + H2O

BALANCING CHEMICAL EQUATIONS

-- Determine the Reaction Occurring

- Reactants

- Products

- Physical States of Each

-- Write an Unbalanced Equation

-- Balance the Equation

- Start with the Most Complex Reactants

- Determine Coefficients Algebraically

- Do Not Change Any Compound Subscripts

Balance the following equations.

a. Ca)OH(2 + HNO3 Ca)NO3(2 + H2O

b. BaCl2 + )NH4(2SO4 BaSO4 + NH4Cl

c. Fe)OH(3 + H2SO4 Fe2)SO4(3 + H2O

d. Na3PO4 + AgNO3 NaNO3 + Ag3PO4

e. Al + Sn)NO3(2 Al)NO3(3 + Sn

f. Na2CO3 + Mg)NO3(2 MgCO3 + NaNO3

g. Al)NO3(3 + H2SO4 Al2 )SO4(3 + HNO3

h. Ba)C2H3O2(2 + )NH4(3PO4

Ba3 )PO4(2 + NH4C2H3O2

Write balanced chemical equations to represent the reactions described by the following statements.

a. Steam )gaseous water( reacts with carbon at high temperatures to produce carbon monoxide )CO( and hydrogen gases.

b. Ethyl alcohol )C2H6O( burns in oxygen to produce carbon dioxide )CO2( and water.

c. Aluminum and sulfur react at elevated temperatures to produce aluminum sulfide )Al2S3(

Balance each of the following chemical equations:

a. C4H10)g( + O2)g( CO2)g( + H2O)g(

b. C6H14)g( + O2)g( CO2)g( + H2O)g(

c. B)s( + Cl2)g( BCl3)l(

d. NO)g( + O2)g( NO2)g(

e. Ti2O3)s( + CO2)g( Ti2)CO3(3)s(

f. OF2)g( O2)g( + F2)g(

g. NaClO3)s( NaCl)s( + O2)g(

h. Al)OH(3)s( Al2O3)g( + H2O)l(

Balance each of the following chemical equations

a. Br2)l( + KI)aq( KBr)aq( + I2)s(

b. Co)s( + O2 Co2O3)s(

c. P4)s( + O2)g( P4O10)s(

d. Al)s( + HNO3)aq( Al)NO3(3)aq( + H2)g(

e. PBr3)l( + H2O)l( H3PO3)aq( + HBr)aq(

f. NO)g( + O2)g( NO2)g(

g. C2H6)g( + O2)g( CO2)g( + H2O)g(

h. CuO)s( + H2SO4)aq( CuSO4)aq( + H2O)l(

STOICHIOMETRY

Stoichiometry is the relationship of quantities of reactants consumed and products made in a chemical reaction.

MoleA mole is the number of atoms in exactly 12 grams of carbon 12.

One mole of any substance contains 6.022 x 1023 atoms )Avogadro’s number( of that substance.

The mass of one mole of an element is the weighted average atomic mass of that element OR the total of all the element masses in a compound or chemical formula.

Calculations Based on Chemical Equations - Stoichiometry

Chemical stoichiometry is the study of the quantitative relationships among reactants and products in a chemical reaction.

Particles

Of A

Particles

Of B

Moles

Of A

Grams

Of A

Moles

Of B

Grams

Of B

Avogadro’s Avogadro’s

number number

formula

subscript

molar molarmass mass

EQUATIONS and the MOLE CONCEPTMoles of equation moles of

Substance A coefficients substance B

Coefficients give the numerical relationships among formula units consumed and/or produced in a chemical reaction.

P4O10 + 6 H2O 4 H3PO4

3 mole to mole relations:

1 mole P4O10 produces 4 moles of H3PO4

6 mole H2O produces 4 moles of H3PO4

1 mole of P4O10 produces 6 moles of H2ONow write dimensional analysis factors:

1 mole P4O10 and 4 moles H3PO4

4 moles H3PO4 1 mole P4O10

OR---------?

Give a word interpretation of the balanced equation

a. 4 NH3 + 3 O2 2 N2 + 6 H2O

b. CS2 + 3 O2 CO2 + 2 SO2

in terms of )a( molecules and )b( moles

Write the twelve mole-to-mole conversion factors that can be derived from the balanced equation

a. 3 HNO2 2 NO + HNO3 + H2O

b. N2H4 + 2 H2O2 N2 + 4 H2O

How many moles of the first-listed product in each of the following equations could be obtained by reacting 0.750 mole of the first-listed reactant with an excess of the other reactant?

a. H2O2 + H2S 2H2O + S

b. 4NH3 + 3O2 2N2 + 6H2O

c. Mg + 2HCl MgCl2 + H2

d. 6HCl + 2Al 3H2 + 2AlCl3

e. SiO2 + 3C 2CO + SiC

f. 5O2 + C3H8 3CO2 + 4H2O

g. CH4 + 4Cl2 4HCl + CCl4

h. 3NO2 + H2O 2HNO3 + NO

Given the equation

4NH3)g( + 5O2)g( 4NO)g( + 6H2O)g(

a. How many moles of O2 are needed to produce 1.34 moles of NO?

b. How many moles of H2O will be produced from 0.789 mole of NH3?

c. How many moles of NH3 are needed to react with 3.22 moles of O2?

d. How many moles of NO are produced when 0.763 mole of H2O is produced?

Given the equation

C3H8)g( + 5O2)g( 3CO2)g( + 4H2O)g(

a. How many moles of O2 are needed to produce 2.38 moles of H2O?

b. How many moles of CO2 will be produced form 0.57 mole of C3H8?

c. How many moles of C3H8 are needed to react with 1.45 moles of O2?

d. How many moles of CO2 are produced when 1.11 moles of H2O are produced?

STOICHIOMETRIC CALCULATIONS

of Masses/Moles

Use Dimensional Analysis

Balance the reaction equation

Convert known masses to moles

Set up mole ratios from the equation

Calculate Moles of desired product or reactant

Convert from moles to mass as required

One way to remove gaseous carbon dioxide )CO2( form the air in a spacecraft is to let canisters of solid lithium hydroxide )LiOH( absorb it according to the reaction.

CO2)g( + 2LiOH)s( Li2CO3)s( + H2O)l(

a. How many grams of LiOH are needed to react

with 1.30 moles of CO2?

b. How many grams of H2O are obtained when

2.50 moles of CO2 react?

c. How many grams of Li2CO3 are produced when

0.500 mole of H2O is produced?

d. How many grams of LiOH must react in order

to produce 12.0 moles of Li2CO3?

How many grams of the first reactant in each of the following equations would be needed to produce 2.00 g of O2?

a. OF2 + H2O O2 + 2HF

b. 2Na2O2 + 2CO2 2Na2CO3 + O2

c. 4C3H5O9N3 12CO2 + 6N2 + O2 + 10H2O

d. 2ClO2 + Na2O2 2NaClO2 + O2

How many grams of the first reactant in each of the following equations would be needed to produce 3.00 g of O2?

a. 4NH3 + 3O2 2N2 + 6H2O

b. (NH4)2Cr2O7 Cr2O3 + N2 + 4H2O

c. N2H4 + 2H2O2 N2 + 4H2O

d. 4C3H5O9N3 12CO2 + 6N2 + O2 +10H2O

Pure silver metal results when silver carbonate )Ag2CO3( is decomposed by heating as shown by the equation

2Ag2CO3 4Ag + 2CO2 + O2

Based on this equation, how many grams of Ag2CO3 must be decomposed to produce each of the following?

a. 1.50 moles of O2

b. 1 billion )1.00 x 109( molecules of CO2

c. 100.0 g of O2

d. 115,000 atoms of Ag

A common method for producing lime )CaO( is the thermal decomposition of limestone )CaCO3(

CaCO3 CaO + CO2

Based on this equation, how many grams of CaCO3

must be decomposed to produce each of the following?

a. 3.00 moles of CO2

b. 3.00 x 1020 molecules of CO2

c. 0.627 g of CaO

d. 125 formula units of CaO

20 copies

Title page Instructions

21 copies

Data sheets

40 copies(2 X 20)

Graph paper

76 copies(4 X 19)

An assembled Handoutexperiment

4 sheetsOf graphpaper

2 data sheets1 sheetOf instructions1 title page

THE LIMITING REACTANT CONCEPT

The limiting reactant is the reactant in a chemical reaction that determines how much product(s) can be formed

LIMITING REACTANTSSTOICHIOMETRIC CALCULATIONS

of Masses/ Moles

Use Dimensional Analysis

Balance the reaction equation

Convert known masses to moles

Determine the limiting Reactant

Set up mole ratios from the equation

Calculate Moles of desired product or reactant

Convert from moles to mass as required

Grams of First reactant, A Grams of Second reactant, B

Moles of A Moles of B

Moles of Product

Grams of product

Compare ratio of moles of A present to moles of B present With mole ratio from balanced chemical equation

Molar mass

Molar mass

Molar mass

Balanced chemical equationUsing limiting reagent

Using each o f the following equations, calculate the number of moles of the first-listed reactant that are needed to produce 4.00 moles of CO2

a. 3O2 + CS2 CO2 + 2SO2

b. FeO + CO Fe + CO2

c. 2C8H18 + 25O2 16CO2 + 18H2O

d. Fe3O4 + CO 3FeO + CO2

Using each o f the following equations, calculate the number of moles of the first-listed reactant that are needed to produce 3.00 moles of CO2

a. C7H16 + 11O2 7CO2 + 8H2O

b. 2HCl + CaCO3 CaCl2 + CO2 + H2O

c. Na2SO4 + 2C Na2S + 2CO2

d. 4Na2CO3 + Fe3Br8 8NaBr + 4CO2 + Fe3O4

Limiting Reactant:Magnesium nitride can be prepared by the direct reaction of the elements as shown by the equation.

3Mg + N2 Mg3N2

For each of the following combinations of reactants, decide which is the limiting reagent.

a. 2.00 moles of Mg and 0.500 moles of N2

b. 3.00 moles of Mg and 1.25 moles of N2

c. 3.00 g of Mg and 0.100 moles of N2

d. 20.00 g of Mg and 7.00 g of N2

Under appropriate conditions water can be produced form the reaction of the elements hydrogen and oxygen as shown by the equation

2H2 + O2 2H2O

For each of the following combinations of reactants decide which is the limiting reactant.

a. 1.75 moles of H2 and 1.00 mole of O2

b. 2.50 moles of H2 and 2.00 moles of O2

c. 6.00 g of H2 and 1.25 moles of O2

How many grams of ZnCl2 can be produced form the reaction of 10.0 g of Zn and 10.0 g of HCl according to the following reaction?

Zn + 2HCl ZnCl2 + H2

Determine the number of grams of each of the products that can be made form 8.00 g of SCl2 and 4.00 g of NaF by the reaction.

3SCl2 + 4NaF SF4 + S2Cl2 + 4NaCl

For the balanced reaction below, answer the following questions:

H2O2 + H2S 2H2O + S1. How many moles of water are produced from 0.5 moles of H2S?

a. 0.5 b. 1 c. 2 d. 2.52. What is the % yield if only 31 grams of S is produced from reacting 34 grams of H2S with an excess of H2O2?

a. 100 b. 91 c. 49 d. 973. How many grams of CO can be produced from the reaction of 10.0 grams of ZnO and 50.0 grams of C according to the following balanced equation? Show all Work

ZnO)s( + C)s( Zn)s( + CO)g(

SIMULTANEOUS ANDCONSECUTIVE REACTIONS

When two or more reactions are involved in stoichiometric calculations, each molar relationship must be taken into account.

Example:In steel making, a three step process leads to

conversion of Fe2O3 into metallic Fe.

3Fe2O3 + CO 2Fe3O4 + CO2

Fe3O4 + CO 3FeO + CO2

FeO + CO Fe + CO2

How many grams of Fe are produced from 500.0 grams of Fe2O3?

WANT = HAVE X CONVERSIONS

32

43

32

3232 OFe moles 3

OFe moles 2

OFe g 159.7

OFe mole 1 x OFe g Fe g

Fe g 9.359Fe mole 1

Fe g 55.85

FeO mole 1

Fe mole 1

OFe mole 1

FeO moles 3

43

WANT = HAVE X CONVERSION FACTORS

Determine the number of grams of each of the products that can be made from 8.0 grams of SCl2 and 4.00 grams of NaF by the reaction.

3SCl2 + 4NaF SF4 + S2Cl2 + 4NaCl

In steelmaking, a three-step process leads to conversion of Fe2O3 into metallic Fe.

3 Fe2O3 + CO 2 Fe3O4 + CO2

Fe3O4 + CO 3 FeO + CO2

FeO + CO Fe + CO2

How many grams Fe are produced from 500.0 grams of Fe2O3?

Simultaneous reactionsA mixture of composition 60% ZnS and 40% CuS is heated in air until the sulfides are completely converted to oxides as shown by the following equations.

2ZnS + 3O2 2ZnO + 2SO2

2CuS + 3O2 2CuO + 2SO2

How many grams of SO2 are produced from reaction of 82.5 g of the sulfide mixture?

Simultaneous reactionsA mixture of composition 50.0% H2S and 50.0% CH4 is reacted with oxygen, producing SO2, CO2 and H2O. The equations for the reactions are

2H2S + 3O2 2SO2 + 2H2O

CH4 + 2O2 CO2 + 2H2O

How many grams of H2O are produced from the reaction of 65.0 g of mixture?

Consecutive ReactionsHow many grams of SO2 can be obtained form 50.0 g of KClO3 by the following two-step chemical process?

2KClO3 2KCl + 3O2

S + O2 SO2

NO2 is a reddish brown gas that is a component of smog. It is formed in the following two-step process.

N2 + O2 2NO

2NO + O2 2NO2

How many grams of NO2 result from the reaction of 2.00 g of N2?

PRODUCT YIELDTHEORETICAL YIELD is the maximum amount of products from the reactants.

ACTUAL YIELD is the amount of product achieved in the experiment

low% yield: side reactions

product lost

high % yield: product contamination, e.g. water

100%x yield ltheoretica

yield actual yieldPercent 100%x

yield ltheoretica

yield actual yieldPercent

Theoretical and Percent YieldBecause of “sloppiness” in his procedures, a student was able to isolate only 16.0 g of a desired product from a chemical reaction rather than the 52.0 g that was theoretically possible. What was the percent yield of product that the student obtained?

The theoretical yield of product for a particular reaction is 25.31 g. A very “meticulous” student isolates 24.79 g of product when the reaction is run. What is the percent yield that this student obtained?

Theoretical and Percent YieldAluminum and sulfur react at elevated temperatures to form aluminum sulfide as shown by the equation.

2Al + 3S Al2S3

In a certain experiment, 125 g of Al2S3 was produced from 75.0 g of Al and 300.0 g of S.

a. What is the theoretical yield of Al2S3

b. What is the percent yield of Al2S3

5.000 g of Ag2S was produced form 5.000 g of Ag and an excess of S according to the reaction

2 Ag + S Ag2S

What is the percent yield of Ag2S?