CH 7: CHEMICAL REACTIONS
TN Ch 7.1 Date
Title and
Highlight
Topic:
EQ:
Write Question out (left side of red line) and answer
it (Highlight answer) based on from what you read.
• Write out the notes from my website.
• You may use different color pens.
• Use Bullets or Number notes.
• Space out your notes so you can add any
additional into during lecture.
NO HIGHLIGTING, UNDERLINING, etc
WE WILL DO OUR FOCUS NOTES
TOGETHER
• Write 2-3 sentences (end of notes) from what
you learned from reading, notes, and/or lecture.
Right Side – NOTES ONLY
TN Ch 5.11
Title and
Highlight
DRAW ANY PICTURES, FIGURES,
AND WRITE OUT ANY PRACTICE
PROBLEMS/QUESTIONS.
WE WILL ANSWER THEM TOGETHER.
LEAVE SPACES SO WE CAN ANSWER
QUES.
LEFT Side – PICTURES, PRACTICE PROBLEMS, ETC
CH 7.1-7.2: CHEMICAL REACTIONS
Topic: Evidence of Chem Reaction
EQ: What evidence can you see
that a chem reaction has
occurred?
READ Ch 7.1-7.2 (pg. 205-209)
Write Questions & Answer Questions #1-3
(notes side) Highlight answer
• Chemical reactions take place all around us and even inside us.
• They are involved in many of the products we use daily.
• If we could see the atoms and molecules that
compose matter, we could easily identify a
chemical reaction:
• Atoms combine with other atoms to form
compounds.
• Original molecules decompose.
• Atoms in one molecule change places with
atoms in another.
• We could know a chemical reaction has
occurred by observing these changes.
• Just remember Ch 3… a chemical change
(reaction) produced something new!!
EVIDENCE OF A CHEMICAL REACTION (VERY IMPORTANT!!!)
The following 5 provides evidence (can see
with our eyes) of a chemical reaction:
• A color change
• The formation of a solid (precipitate)
• The formation of a gas, smoke,
odor, bubbles
• The emission of light
• The emission or absorption of heat
EVIDENCE OF A CHEMICAL REACTION
EVIDENCE OF A CHEMICAL REACTION
NOT EVIDENCE OF A CHEMICAL
REACTION
• We can be fooled.
• When water boils, bubbles form and a gas is evolved, but no chemical reaction has occurred.
• Boiling water forms gaseous steam (still water) - no chemical change has occurred.
PRACTICE PROBLEMS #1:
• Which changes involve a chemical reaction? EXPLAIN!!
A. ice melting
B. An electric current passing through water, resulting in formation of H and O gases.
C. Iron rusting
D. Bubbles forming when a soda can is opened.
Left side
PRACTICE PROBLEMS #2:
• Which changes involve a chemical reaction? EXPLAIN!!
A. Butane burning in a lighter
B. Butane evaporating out of a lighter
C. Wood burning
D. Dry ice subliming (turns from solid to gas)
Left side
CH 7.3: CHEMICAL EQUATIONS
Topic: Chem Equation
EQ: What are the rules for
writing a balanced chem
equation?
READ Ch 7.3 (pg. 210-211)
Write Questions & Answer Questions #4-6
(notes side) Highlight answer
CH. 7.3 NOTES -- CHEMICAL REACTIONS
•We represent chemical reactions with chemical equations.
•Chemical equations give information about the REACTANTS & PRODUCTS
Review: Reactants: ______ side of the arrow.
Products: __________ side.
Example of a Balanced Chemical Equation:
2H2 (g) + O2 (g) 2H2O (g)
States of Matter (S.O.M.) - each chemical has it in parentheses next to the formula.
left
right
COMMON SYMBOLS USED IN CHEMICAL EQUATIONS
(See Table 7.1)
+ = used to separate 2 reactants or 2 products from each other
→ = “yields” or “reacts to produce”
= _____________ reaction (like a rechargeable battery)
(s) (l) (g) (aq) = phase of matter: (solid, liquid, gas, or “aqueous”)
= ___________ supplied to the reaction
MnO2 = a catalyst, (in this case, MnO2), is used to ________ ____
the reaction.
reversible
heat
speed up
BALANCING CHEMICAL EQUATIONS
Why do you have to balance a chemical equation?
• Law of Conservation of Matter (or Mass): “Matter is neither
____________ nor _______________ in chemical reactions, ITS
CONSERVED (REARRANGED)!!!.”
• During a chemical reaction, atoms are either _________,
______________, or rearranged. The _____________ and type of
each atom stays the same.
How do you balance a chemical equation?
• __________________ are placed in front of the substances to get
the same number of atoms of each element on both sides of the
equation.
created destroyed
joined
separated number
Coefficients
DO YOU KNOW HOW TO COUNT? Practice Problem #1
How many atoms of each element are there in each compound?
a) Ca(OH)2 ___
b) C3H8O___
c) (NH4)2HPO4 ___
d) HC2H3O2 ___
Left side
RULES - Balance a chemical equation
• Use Atom inventory:
(This is how you show your work) • Split the equation in half (under the arrow) and
list the elements. • Count # atoms you see on both the reactant
AND product side. • If all atoms on each side are equal, then the
equation is called a “balanced chemical equation”
• If not (most of the time), then you must balance the equation by adding coefficients (BIG #’s in the front of chemicals.
THE CHEMICAL EQUATION: COMBUSTION OF METHANE
• We represent this skeleton (unbalanced – no coefficents) reaction with the following equation:
• With states included, the equation becomes
The left side of the equation has two oxygen atoms and the
right side has three.
Atoms cannot simply appear or disappear in chemical
equations. We must account for the atoms on both sides of the
equation.
Draw Pics also with the notes!!
To correct these problems, we must create a balanced equation.
The equation is now balanced because
the #’s of each type of atom on both sides
of the equation are equal.
(AKA…Law of Cons. of Matter is valid!!!)
Draw Pics also with the notes!!
CHECKING THE BALANCED EQUATION
• If there are no coefficients, a 1 is implied (but we never write 1’s).
• The balanced equation is as follows:
Coefficients can only be placed ___ _________ of a chemical formula.
Practice Problem #2: How many atoms of each type are indicated in the following compounds? (a) 2 (NH4)3PO4 N= ___ H= ___ P= ___ O= ___
(b) 4 KC2H3O2 K= ___ C= ___ H= ___ O= ___
(c) 3 Ca(NO3)2 Ca= ___ N= ___ O= ___
in front
Left side
RULES FOR BALANCING CHEMICAL EQUATIONS (1) You cannot change a ________________!!
Example : H2 + O2 H2O
To balance oxygen, you cannot change water’s formula to_________!
(2) You cannot place the coefficient in the ______________ of a formula!!
Example : Al + N2 AlN
To balance nitrogen, you cannot put a 2 in the middle to make _______.
(3) Reduce the coefficients to the simplest ____________ ___ ratio.
Example: 4H2 + 2O2 4H2O can be reduced to…
__H2 + __O2 __H2O
subscript
H2O2
middle
Al2N
2 2
2 2
2 1 2
whole #
Practice Problem #3: Balance Equations by adding coefficients
a) ___(NH4)2CO3 ___NH3 + ___CO2 + ___H2O
b) ___Al + ___CuSO4 ___Al2(SO4)3 + ___Cu
c) ___Fe(OH)3 ___Fe2O3 + ___H2O
d) ___Li + ___H2O ___LiOH + ___H2
Left side – leave 5 spaces between questions
CH 7.4: BALANCING EQUATIONS
Topic: Writing Chem Equations
EQ: How do you write a balanced
chem equation with no formulas?
READ Ch 7.4 (pg. 212-214)
Write Questions & Answer Questions #7
(notes side) Highlight answer
HOW TO WRITE BALANCED CHEMICAL EQUATIONS
1.Write a skeleton (unbalanced) equation by writing correct chemical formulas. DON’T FORGET TO BALANCE THE CHARGES!! (Use Polyatomic card)
2. Once you have written all formulas, write in your S.O.M. (as many as possible).
3. Balance the equation by adding COEFFICIENTS (BIG #’s in the front).
4. VERY IMPORTANT!!...you can change only the coefficients to balance a chemical equation; never change the subscripts.
5. Rewrite final balanced equation at the end of problem (and highlight)
Practice Problem #1: Write a skeleton equation from
words:
Solid aluminum reacts with aqueous
sulfuric acid to form aqueous aluminum
sulfate and hydrogen gas
Left side – leave 5 spaces between questions
Practice Problem #2: Write a skeleton equation from
words:
Sodium reacts bromine, when heated, reacts
to produce solid sodium bromide
Left side – leave 5 spaces between questions
WRITING SKELETON EQUATIONS
Practice Problem #3: Write the following equations into words using
complete sentences.
a) NaHCO3 (s) + HCl (aq) NaCl (aq) + H2O (l) + CO2 (g)
b) H2SO4 (aq) + BaCl2 (aq) HCl (aq) + BaSO4 (s)
Left side – leave 5 spaces between questions
CH 7.5: BALANCING EQUATIONS
Topic: Aqueous Solutions
EQ: How do you determine if a
solution is aqueous?
READ Ch 7.5 (pg. 214-217)
Write Questions & Answer Questions #8-13
(notes side) Highlight answer
• soluble – a compound that dissolves in that liquid.
• insoluble - does not dissolve in the liquid.
• An aqueous solution is a homogeneous mixture (solution) of a substance with water.
• When ionic compounds dissolve in water, they usually dissociate (break apart) into their component ions.
The Light Bulb Demonstration
bright glow weak glow no glow
Strong Electrolyte Weak Electrolyte Nonelectrolyte
• 100% completely
dissociate into ions
•Types: Ionic
Compounds, Strong
Acids & Bases
• Examples: salt water,
. HCl, drain cleaner
• partially (not
100%) dissociate
into ions
• Types: Weak
Acids & Bases
•Examples: tap
water, vinegar
• no dissociation
• Examples: pure
(DI) water, sugar in
water, oil, alcohol
AQUEOUS SOLUTIONS: NOT ALL DISSOLVE IN WATER
• Not all ionic compounds dissolve in water.
• AgCl does not dissolve in water.
• AgCl remains as a solid, AgCl(s), within the liquid water.
• It does not dissolve or dissociate into ions.
SOLUBILITY RULES: MUY IMPORTANTE!!
SO…..
If not all ionic compounds dissolve, then how do we know without performing experiments?
We use solubility rules.
SO
LUB
ILIT
Y R
ULE
S C
HA
RT
AN
Y C
OM
PO
UN
D N
OT
LISTE
D IN
TH
ESE G
EN
ER
AL
RU
LES IS
CO
NSID
ER
ED
IN
SO
LUB
LE. Any
compound
that
contains
these ions
is always
soluble
except
with the
ions listed
Any
compound
that
contains
these ions
is never
soluble
except
with the
ions listed
WILL BE GIVEN TO YOU ON TESTS!!
SOLUBILITY: MOSTLY INSOLUBLE
Note that the solubility rules contain many exceptions.
Let’s practice how to read the
chart
Look at carbonate (CO3 -2)
SOLUBILITY: MOSTLY INSOLUBLE
Exceptions.
For example:
• compounds containing the CO32− ion are insoluble.
• CaCO3, FeCO3, SrCO3, and CuCO3 = do not
dissolve in water. (SOLIDS)
• HOWEVER - compounds containing CO32− are
soluble when paired with Li+, Na+, K+, or NH4+.
• Li2CO3, Na2CO3, K2CO3, and (NH4)2CO3 are
soluble. = a.q.
PRACTICE PROBLEMS #1
• Practice using the solubility rules for the following compounds:
• Ca(NO3)2
• AgCl
• Ni(OH)2
Left side
PRACTICE PROBLEMS #2
Which of the following are soluble in water? a. SrSO4
b. NaNO3
c. PbCl2
d. AgBr
e. CaCl2
f. Pb(NO3)2
g. PbSO4
Left side
CH 7.6
Topic: Precipitate Rxn
EQ: How do we determine
the products of a precip. rxn?
READ Ch 7.6 (pg. 218-221)
Write Questions & Answer Questions #14-15
(notes side) Highlight answer
•Precipitate reactions (rxn), reactions that form a solid (s), called a precipitate, upon mixing two aqueous solutions.
•Also called Double Replacement (DR) reactions
DR/Precipitate Rxns:
•A reaction between _____ ________________ that are (aq) that produces _____ ________________ , one of which is _____________(produces s, l, or g)
• THINK FOIL!!
General Form: ____ + ____ ____ + ____
A solid produced during a chemical reaction is called a precipitate.
two compounds
two compounds
insoluble
AX(aq) BY(aq) AY(aq) BX(s)
+ +
PREDICT THE PRODUCTS OF THE FOLLOWING REACTION: (NEED
SOLUBILITY RULES!!)
Pb(NO3)2(aq) + KI (aq)
Pb(NO3)2(aq) + 2KI (aq) PbI2(s) + 2KNO3 (aq)
We know it is a solid precipitate because it is insoluble (solid) according to the solubility rules.
Precipitation
• a brilliant yellow precipitate of PbI2(s) forms.
What about….. Na Cl (aq) + KI (aq)
NaCl (aq) + KI (aq) NaI(aq) + KCl (aq) (BORING RXN!) So, if no reaction occurs….. NaCl (aq) + KI (aq) NR (no reaction)
No precipitate, liquid, or gas forms, which means no reaction.
• Precipitation reactions do not always occur when mixing two aqueous solutions.
• Sometimes…no reaction occurs.
PREDICTING PRECIPITATION REACTIONS
• The key to DR/ Precipitate reactions is only insoluble (solids) compounds form precipitates.
Rules:
1. Write a skeleton equation
2. Combine the cation (+) from one reactant with the anion (-) from the other. (THINK FOIL!!!)
Balance charges - formulas for the new products.
WRITING EQUATIONS FOR PRECIPITATION REACTIONS
3. Use the solubility rules - determine whether any of new products are insoluble = solid.
4. If all products are (aq) = soluble, there will be no precipitate. Write NO REACTION (NR) next to the arrow. (Still have to write reactants!!)
WRITING EQUATIONS FOR PRECIPITATION REACTIONS
Example: Solutions of sodium carbonate Na2CO3(aq)
and copper(II) chloride CuCl2(aq) are mixed. (Balance your charges)
Na2CO3(aq) + CuCl2(aq) → CuCO3(s) + NaCl(aq)
(This is only a skeleton rxn. We still need to……)
WRITING EQUATIONS FOR PRECIPITATION REACTIONS
Balance the equation.
• Only adjust coefficients, not the subscripts.
Na2CO3(aq) + CuCl2(aq) → CuCO3(s) + 2 NaCl(aq)
CH 7.8-7.9 (PART 1)
Topic: Types of Reactions
EQ: What is the difference
between the 8 types of Rxns?
READ Ch 7.8-7.9 (pg. 223-228)
Write Questions & Answer Questions #17-19
(notes side) Highlight answer
GENERAL TYPES OF REACTIONS (CONTINUED)
1) _______________ Replacement:
A reaction between _____ ________________ that are dissolved in water that produces _____ ________________ , one of which is ________________ (s, l, or gas) .
General Form: ____ + ____ ____ + ____
2) A solid produced during a chemical reaction is called a precipitate.
Examples: CaCl2 (aq) + AgNO3 (aq) _________ + ________
NaOH (aq) + HCl (aq) ________ + ________
Double
two compounds
two compounds insoluble
AX(aq) BY(aq) AY(aq) BX(s)
+ +
CH 7.8 ACID–BASE REACTIONS
• 3) Acid–base reactions are reactions that form water and a salt (Ionic Compound).
Also called neutralization reactions.
SOME COMMON ACIDS AND BASES
PRACTICE PROBLEMS #1
• Write a balance equation for the following:
HNO3 + Ca(OH)2
Left side
GAS EVOLUTION REACTIONS:
4. Gas Evolution Rxns – produce a GAS!!!
1. Write a skeletal equation
HNO3(aq) + Na2CO3(aq) → H2CO3(aq) + NaNO3(aq)
(If you form this..ding ding!!)
2.You must recognize that H2CO3(aq) decomposes into H2O(l) and CO2(g) and write the corresponding equation.
HNO3(aq) + Na2CO3(aq) → H2O(l) + CO2(g) + NaNO3(aq)
3. Finally, balance the equation.
2 HNO3(aq) + Na2CO3(aq) → H2O(l) + CO2(g) + 2NaNO3(aq)
PRACTICE PROBLEM #2
• Write a balance equation for the following:
hydrobromic acid + potassium sulfite (aq)
Left side
GAS EVOLUTION REACTIONS
CH 7.8-7.9 (PART 2)
Topic: Types of Reactions
EQ: What is the difference
between the 8 types of Rxns?
READ Ch 7.8-7.9 (pg. 223-228)
Write Questions & Answer Questions #21, 23
(notes side) Highlight answer
CH 7.8 SEVEN TYPES OF REACTIONS
5)_______________: (sometimes called “Synthesis”)
• A reaction of _____ __________________, typically a metal and a nonmetal to form ______ ______________.
• It is the opposite of decomposition.
General Form: ___ + ___ _____
Examples: Al (s) + Cl2 (g) _______
PbO (s) + H2O (l) ______
Combination
two substances
one compound
A X AX
+
TYPES OF REACTIONS
6) ________________________:
• A reaction that breaks apart ______ ______________ into simpler substances, (usually two elements or an element and a smaller compound.)
General Form: _____ ___ + ___
Examples: H2O _____ + _____
KCl ___ + _____
Remember that “H,N,O,F,Cl,Br,I” elements are diatomic when alone!!
Decomposition
one compound
AX A X +
GENERAL TYPES OF REACTIONS (CONTINUED)
7) _________________: Reacts with oxygen gas!!!
• Combustion reactions are exothermic (they emit heat).
• A reaction between a Carbon/Hydrogen with _____ always produces the same… ________ + ________
• This reaction is too easy!! Don’t miss it!
General Form: CxHy + O2 ____ + ____
Examples: C2H2 + O2 _______ + _______
C7H6O + O2 _______ + _______
Combustion
O2 CO2 H2O
CO2 H2O
BALANCING EQUATIONS:COMBUSTION
___Al + ___O2
___ S + ___O2
Left side – Leave space to show work
PRACTICE PROBLEM #1
CH 7.8-7.9 (PART 3)
Topic: Types of Reactions
EQ: What is the difference
between the 8 types of Rxns?
READ Ch 7.8-7.9 (pg. 223-228)
Write Questions & Answer Questions #24
(notes side) Highlight answer
GENERAL TYPES OF REACTIONS (CONTINUED)
8) _____________ Replacement:
• A reaction between ____ ______________ and ___ ____________ that produces a different _____________ and ______________.
• General Forms:
____ + __ ____ + __
• The element that is trying to replace the other must be ________ _______________ than the one it is replacing.
• You must use the Activity Series to see if the reaction will happen.
• See chart _________ ___ = more reactive
Single
one compound one element
compound element
Y X AX AY
more reactive
Higher up
+
ACTIVITY SERIES
SINGLE REPLACEMENT REACTIONS
NaCl + F2 _____ + _____
FeCl2 + K _____ + _____
HCl + Zn _____ + _____
HCl + Au _____ + _____
H2O + Na _____ + _____
H2O + Fe _____ + _____
AgNO3 + Cu _____ + _____
Left side – Leave space to show work
PRACTICE PROBLEM #1
CH 7.10
Topic: Types of Reactions
EQ: What are all 8 types of
Rxns?
READ Ch 7.10 (pg. 228-232)
NO BQ’s
8 TYPES OF REACTIONS:
Let’s Review
• Combination (also called synthesis)
• Decomposition
• Combustion
• Single Replacement
• Double Replacement
• Acid/Base
• Precipitate
• Gas Evolution
CH 7.7
SKIP!!
CH 7.7 : MOLECULAR AND COMPLETE IONIC
EQUATIONS There are rxns that occur where not ALL ions participate. • Some ions do all the work and some ions just
watch the show happen.
• To show this is an equation, we write a net-ionic equation:
• A “net ionic equation” only shows the ions that were used to make the precipitate (solid).
• Basically shows only the ions doing all the work to make the precipitate and gets rid of the useless ions.
CH 7.7 : MOLECULAR AND COMPLETE IONIC EQUATIONS
• 1st Step: Need a molecular equation (also called BALANCED equation)
• AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
• 2nd Step: Write an Ionic equation - shows all (aq) ionic compounds dissociated in solution. (Break them apart) Separate only (aq) into their ions. Do NOT separate any solid, liquid, or gas
compounds. They DO NOT dissociate!!
Ag+(aq) + NO3
−(aq) + Na+(aq) + Cl−(aq) → AgCl(s) + Na+(aq) + NO3–(aq)
SPECATOR IONS
• In the ionic equation, some of the ions in solution appear unchanged on both sides of the equation.
• These ions are called spectator ions because they do not participate in the reaction. (Basically they do nothing in the reaction)
WRITING CHEMICAL EQUATIONS FOR REACTIONS IN SOLUTION:
COMPLETE IONIC AND NET IONIC EQUATIONS
• 3rd Step: Cross out ALL spectator ions.
• ***To cross out, you must have same amount on each side.
• Equations such as this one, which show only the ions that actually participate in the reaction, are called net ionic equations.
Ag+(aq) + Cl− (aq) → AgCl(s)
Remember this reaction from earlier section:
Pb(NO3)2(aq) + 2KI (aq) PbI2(s) + 2KNO3 (aq)
Write the ionic and
net-ionic equations
A PICTURE OF THE REACTION:
Because K+ and NO3
- are spectator ions and are not included in the net ionic equation.
Net Ionic Equation Pb2+ (aq) + 2I-(aq) PbI2(s)
Pb2+ NO3-
NO3-
NO3-
K+ I- K+
PbI2(s)
DIFFERENCE BETWEEN MOLECULAR, COMPLETE IONIC, AND NET IONIC
EQUATIONS
To summarize:
A molecular (Balanced) equation is a chemical equation showing the complete, neutral formulas for every compound in a reaction.
An ionic equation is a chemical equation showing all of the species as they are actually present in solution.
A net ionic equation is an equation showing only the species that actually participate in the reaction.
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