#20 Write a balanced equation for the complete combustion
of each compound:
a. formic acid: HCOOH
2HCOOH + O2
2 H2O
+ 2 CO2
b. heptane: C7H16
C7H16+ 11O2
8 H2O
+ 7CO2
21. Write a balanced equation for the complete combustion of
glucose: C6H12O6
C6H12O6
+ 6 O2
6 H2O + 6 CO2
#22 What are the five types of chemical reactions?
#23 What are the keys to predicting the products of the five
general types of reactions?
1. combination: Two elements combine to form one new
compound.
2. decomposition: one compound breaks up into its elements.
3. single replacement: one element replaces another in a
compound.
4. double replacement: two compounds exchange ions to form
two new compounds.
5. combustion: a fuel reacts with oxygen gas to form carbon
dioxide and water vapor.
#24 Classify each reaction and balance the equations:
a.
2 C3H6
+ 9 O2  63 CO2
+63 H2O
combustion
b.
2 Al(OH)3

Al2O3
+ 3 H2O
decomposition
c.
d.
4 Li + O2
 2 Li2O
combination
Zn
+ 2 AgNO3
single replacement
 2Ag
+
Zn(NO3)2
#25 Which of the five general types of reactions would most
likely occur, given each set of reactants? What are the probable
products?
a. an aqueous solution of two ionic compouds
double replacement is most likely. The most likely products
are two new compounds.
b. a single compound
a decomposition is most likely. The elements from which this
compound is composed are the likely products.
c. two elements
a combination is most likely. The likely product will be a
“combination” of the two elements
d. oxygen and a compound of carbon and hydrogen
combustion. The likely products are CO2 and H2O
#26 complete and balance an equation for each reaction:
a. CaI2
+
Hg(NO3)2

a. CaI2
+
Hg(NO3)2
 HgI2(s)
?
(HgI2 precipiates)
+
Ca(NO3)2
b. Al + Cl2

?
b. 2Al + 3Cl2

2AlCl3
c.
Ag
c. 2Ag
d. C2H2
+

HCl
+
2HCl
+
O2
d. 2C2H2
e. MgCl2 
e. MgCl2
?

2AgCl

+
+
?
5O2

4CO2
?

H2(g)
Mg
+
Cl2
+
2H2O
#27 What are the three types of products that result in
double-replacement reactions?