Download Unit 7 - TeacherWeb

Unit 7
Chemical Reactions
Cost: $1
Name: __________________
Period: ________
Atom Counting
=H
=O
=C
1. Write the formula that corresponds to each of the following samples. Then describe the sample
using the terms we have learned in class.
sample
formula
2. Given the formulas below give the number of each type of atom present.
formula
atoms present
3 N2O + N2
N ______
5 Ca(NO3)2 + 2 O2
Ca ______
5 C3H8O + 3 CO2
C ______
O ______
N ______
H ______
O ______
O ______
3. Draw an atomic level picture that represents a chemical change.
before
after
1
Balancing Reactions Practice 2
1.
2 C + O2

In the above reaction
2 CO
are the reactants and
This equation could be interpreted by saying that two
with one molecule of
to form
is the product.
of carbon react
molecules of
.
2. In each of the pictures below, represents an oxygen atom while represents a nitrogen
atom. Write the chemical reaction that goes with each picture. The first one is done for
you.
N
2
+
O
2
2 NO
+
+
+
2
Balancing Reactions Practice 2
3. Draw pictures to represent the following chemical reactions.
C + 2 H2
CH4
2 H2 + O2
2 H2O
4. Do an atom inventory to show that each of the following reactions is correctly balanced.
O2 
a.
4 Li +
b.
2 Al +
c.
2 NH3 
2 Li2O
3 Br2 
N2 +
2 AlBr3
3 H2
3
Balancing Reactions Practice 2
Balance the following chemical equations.
a.
Al +
HCl
b.
P4 +
H2
c.
FeCl3 +
d.
As +
e.
Au2S3 +
f.
Al(OH)3 +


Na2S 
Cl2 
AlCl3 +
PH3
Fe2S3 +
NaCl
AsCl5
H2 
HCl
H2
H2S +

Au
AlCl3 +
H2O
4
Balancing Reactions Practice 2
1. Balance each of the following chemical equations.
H2 +
Fe3O4 
Na2SiF6 +
C5H12 +
C6H8O6 +
NaCl +
Fe +

Na
O2
O2
H2O



H2O
Si +
CO2 +
CO2 +
Cl2 +
NaF
H2O
H2O
H2 +
NaOH
5
Balancing Reactions Practice 2
NH3 
PCl3 +
Co2S3 +
H2
SO2 +
O2
PBr5 +
H2O


P(NH2)3 +
Co +
HCl
H2S
SO3

H3PO4 +
HBr
2. Why does a chemical equation have to be balanced in order to be correct?
3. What does a balanced equation tell you about a reaction (2 or 3 things)?
6
Balancing Reactions Practice 2
For each of the following types of reactions classify them as one of the following: Synthesis,
Double Replacement, Single Replacement, Combustion, Decomposition. Then balance each
of the reactions
1. ______________
H2(g) + Cl2(g) 
2. ______________
Al(s) + CuCl2(aq)  AlCl3(aq) + Cu(s)
3. ______________ C8H18(l)
+ O2

HCl(g)
CO2 + H20
4. ______________ KI (aq) + Pb(NO3)2(aq)  PbI2(s) + KNO3(aq)
5. ______________ CaCO3(s)  CaO(s) + CO2(g)
6. ______________
SnCl2(s) + Cl2(g)  SnCl4(s)
7. ______________ NaCl(aq) + AgNO3(aq)  AgCl(s) + NaNO3
8. ______________ CH4(g) + O2(g)
9. ______________
NH4NO3 

CO2(g) + H2O(g)
N20 + H20
10. ______________ Na(s) + H20(l)  NaOH(aq) + H2(g)
For each of the following classify them as one of the types of reactions from above.
11.
12.
7
Extra Practice Worksheet
Directions: Balance the following chemical equations.
1.
Al +
Pb(NO3)2 ---------->
Al(NO3)3 +
2.
Cu +
AgNO3 -----------> Cu(NO3)2 +
3.
K+
H2O ------------->
KOH +
4.
Cl2 +
LiF
LiCl +
F2
5.
Ca(OH)2 +
HCl ----------->
CaCl2 +
H2O
6.
KOH +
H3PO4 ---------->
K3PO4 +
H2O
7.
Al(NO3)3 +
H2SO4 -------->
Al2(SO4)3 +
HNO3
8.
Na2SO3 +
HCl
----------->
NaCl +
9.
KNO3 ------------->
KNO2 +
O2
10.
PbO2 ------------->
PbO +
O2
11.
NaOH ------------>
Na2O +
H2O
12.
MgCO3 ------------>
MgO +
CO2
13.
Na +
Cl2 ----------->
14.
Br2 +
H2O +
15.
CaO +
16.
P2O5 +
17.
KClO3 ---------->
18.
NaOH +
19.
(NH4)2SO4 +
20.
AgCH3COO +
--------------->
Ag
H2
H2O +
SO2
NaCl
SO2 ---------->
H2O ----------->
HBr +
H2SO4
Ca(OH)2
BaO ----------->
KCl +
Ba3(PO4)2
O2
H2SO4 ---------->
Ca(OH)2
Pb
Na2SO4 +
--------->
Na3PO4 --------->
H2O
CaSO4 +
Ag3PO4 +
NH3 +
H2O
NaCH3COO
8
Predicting Products Practice Worksheet #1
Part 1: Identify the type of reaction, predict the products & balance the following chemical
equations.
TYPE: (SR=single replacement, DR=double replacement, D=decomposition, S=synthesis,
C=combustion)
_____ 1.
Al +
Pb(NO3)2 ---------->
_____ 2.
C6H6 +
_____ 3.
H2O ------------>
_____ 4.
MgO ------------>
_____ 5.
C5H8 +
_____ 6.
SO3 ------------>
_____ 7.
Br2 +
_____ 8.
NaOH +
_____ 9.
C3H9OH +
_____ 10.
AgC2H3O2 +
O2
O2
H2O
------------>
------------>
---------->
H2SO4 ---------->
O2
------------>
Zn3(PO4)2 --------->
Part 2: Write a balanced formula equation for each of the following reactions. (Include states)
1. Aluminum metal reacts with solid sulfur to produce solid aluminum sulfide.
2. Solid iron (III) hydroxide decomposes to form solid iron (III) oxide and water.
3. A solution of copper (II) oxide reacts when mixed with a solution of sulfuric acid. The
solution remaining after the reaction contains copper (II) sulfate and water.
4. Propane gas (C3H8) produces carbon dioxide gas and water vapor when burned in the presence
of oxygen gas.
9
Predicting Products Practice Worksheet #2
Determine the type of reaction, then complete and balance the following reactions:
1.
_____________________
KOH +
H3PO4 ---------->
2.
_____________________
Ca(OH)2 +
HCl ----------->
3.
_____________________
Al(NO3)3 +
H2SO4 -------->
4.
_____________________
C5H8 +
5.
_____________________
KNO3 ------------->
6.
_____________________
Fe (III) +
7.
_____________________
Al +
8.
____________________
AgNO3 +
9.
____________________
MgCO3 ------------->
10.
____________________
C3H9OH +
O2 ------------->
O2 --------->
Pb(NO3)2 -------->
K2SO4 ---------->
O2 ---------->
Complete the following word equations and then write them as balanced chemical equations.
1. aluminum nitrate + sodium hydroxide --------->
2. sulfur trioxide ------------>
3. phosphoric acid + magnesium hydroxide --------->
4. ammonium nitrate ------->
10
Balancing Reactions and Types of Reactions
Balancing equations:
1. During a chemical reaction, atoms may be combined, molecules split apart, or atoms rearrange within
molecules. But, atoms cannot be created or destroyed.
2. A balanced equation MUST have EQUAL numbers of EACH type of atom on BOTH sides of the arrow.
3. An equation is balanced by counting atoms on each side of the arrow and then changing the coefficients so
that the total on each side is equal. Note that only the coefficients can be changed, NEVER a subscript.
4. The coefficient times the subscript gives the total number of atoms.
H2
+
O2
→
H2O
1. Start out by taking an atom inventory:
Reactants
H= 2
O= 2
Products
H= 2
O= 1
2. Now add coefficients in a somewhat trial-and-error fashion in order to get equal numbers of each type of atom
on both sides of the arrow.
2H2

+
O2
→
2H2O
By adding a two in front of the H2O we get two oxygen atoms on the product side. However, we also get four
hydrogen atoms so we have to add a two in front of the H2 to get four hydrogen atoms on the reactants side.
Try the following:
Zn + HCl → ZnCl2 + H2
KClO3 → KCl + O2
S8 + F2 → SF6
Fe + O2 → Fe2O3
C2H6 + O2 → CO2 + H2O
Reaction Types: Single Replacement
During single replacement, one element replaces another element in a compound. There are two different possibilities:
1. One cation replaces another. Written using generic symbols, it is: AX + Y → YX + A. Element Y has
replaced A (in the compound AX) to form a new compound YX and the free element A. Remember that A
and Y are both cations (positively-charged ions) in this example. Some examples are (be sure to balance the
reactions):
Cu + AgNO3 → Ag + Cu(NO3)2
Fe + Cu(NO3)2 → Fe(NO3)2 + Cu
11
Ca + H2O → Ca(OH)2 + H2
Zn + HCl → ZnCl2 + H2
2. One anion replaces another. Written using generic symbols, it is: A + XY → XA + Y. Element A has
replaced Y (in the compound XY) to form a new compound XA and the free element Y. Remember that A
and Y are both anions (negatively-charged ions) in this example. Some examples involve halogens, so here
are two examples:
Cl2 + NaBr → NaCl + Br2
Br2 + KI → KBr + I2
Try predicting the products of the following single replacement reactions:
ZnS + O2 →
K + H2O →
Fe + HCl →
NaI + Br2 →
Reaction Types: Double Replacement
Important notes to remember: (1) NONE of the equations are balanced!! and (2) make sure to write correct formulas.
DO NOT just copy the subscripts from the reactants over into the products. During double replacement, the cations
and anions of two different compounds switch places. Written using generic symbols, it is: AB + XY → AY + XB,
where A and X are the cations (positively charged ions) in this example, with B and Y being the anions (negativelycharged ions).
Some examples are:
KOH + H2SO4 → K2SO4 + H2O
FeS + HCl → FeCl2 + H2S
NaCl + H2SO4 → Na2SO4 + HCl
AgNO3 + NaCl → AgCl + NaNO3
Try These:
Ca(OH)2 + HCl →
Al(NO3)3 + H2SO4 →
Pb(NO3)2 + K2S →
Pb(NO3)2 + CuSO4 →
Reaction Types: Decomposition
During decomposition, one compound splits apart into two (or more pieces). These pieces can be elements or simpler
compounds. Written using generic symbols, it is usually shown as:
AB → A + B
However, that really only works for splitting apart into the elements, like these examples.
12
HgO → Hg + O2
H2O → H2 + O2
MgCl2 → Mg + Cl2
FeS → Fe + S
Decomposition can also split one compound into two simpler compounds (or compound and an element) as in these
examples:
CaCO3 → CaO + CO2
Na2CO3 → Na2O + CO2
KClO3 → KCl + O2
Ba(ClO3)2 → BaCl2 + O2
Notice how, in every case so far, there is only one substance on the left-hand (reactant) side. This is always the case in
a decomposition reaction.
Try These:
NaClO3 →
Li2CO3 →
KOH →
NaCl →
Reaction Types: Synthesis
Synthesis are, at this level, almost always the reverse of a decomposition reaction. That means that two pieces join
together to produce one, more complex compound. These pieces can be elements or simpler compounds. Complex
simply means that the product compound has more atoms than the reactant molecules. Usually!!
Written using generic symbols, it is usually shown as:
A + B → AB
These are some examples:
Mg + O2 → MgO
H2 + O2 → H2O
K + Cl2 → KCl
Fe + O2 → Fe2O3
Notice that two elements are combining in each example. Synthesis can also be two compounds making a more
complex compound (or a compound and an element joining together) as in these examples:
CaO + CO2 → CaCO3
Na2O + CO2 → Na2CO3
KCl + O2 → KClO3
Ba(ClO3)2 → BaCl2 + O2
13
Notice how, in every case so far, there is only one substance on the right-hand (product) side. This is not always the
case in a synthesis reaction. Sometimes there will be two products. Here's an example:
CO2 + H2O → C6H12O6 + O2
Here's another example of a synthesis reaction:
H2 + O2 → H2O2
Since synthesis reactions are the reverse of decomposition, you might ask if the decomposition rules apply, just in
reverse. The answer is yes! Try these:
LiCl + O2 →
Na2O + CO2 →
SO3 + H2O →
N2 + H2 →
Reaction Types: Combustion
Combustion, at its most general, can mean the reaction of oxygen gas (O2) with anything. However, we will
understand combustion to mean the reaction of oxygen with a compound containing carbon and hydrogen. A common
synonym for combustion is burn.
Written using generic symbols, it is usually shown as: CxHy + O2 → CO2 + H2O
These are some examples:
CH4 + O2 → CO2 + H2O
C2H6 + O2 → CO2 + H2O
C6H12O6 + O2 → CO2 + H2O
C2H5OH + O2 → CO2 + H2O
Try these:
C6H6 + O2 →
C12H22O11 + O2 →
C25H52 + O2 →
14