1. 1 mole KClO3 X 2KClO3  2KCl + 3O2 6.54 g KClO3 X 3 moles O2
#15 How many molecules of oxygen are produced by the decomposition
of 6.54 g of potassium chlorate
2KClO3  2KCl O2
6.54 g KClO3 (given)
? molecules produced
1 mole KClO3 X
g KClO3
6.54 g KClO3 X 1
3 moles O2
2 mole KClO3
x x 1023 molecules O2
1 mole O2
= 4.82 x 1022 molecules O2 =
molar mass of KClO3

2. 1 mole NO x 3NO2 + H2O  2HNO3 + NO 5.00 x 1022 molecules NO x
#16 The last step in the production of nitric acid is the reaction of
nitrogen dioxide with water.
3NO2 + H2O  2HNO NO
5.00 x 1022 molecules NO (given)
? g NO2
1 mole NO x
6.02 x 1023 molecules NO
5.00 x 1022 molecules NO x 1
3 moles NO2 x
1 mole NO
46 g NO2
1 mole NO2
= 11.5 g NO2
= 46
molar mass of NO2

3. 2CO + O2  2CO2 #17 The equation for the combustion of carbon monoxide
is:
2CO O2  2CO2
How many liters of Oxygen are required to burn 3.86 L of
carbon monoxide?
2CO O2  2CO2
3.86 L CO
? L O2
1 mole CO x
22.4 L CO
1 mole O2 x
2 mole CO
22.4 L O2
1 mole O2
3.86 L CO x 1
= 1.93 L O2

4. P4(s) + 6H2(g)  4PH3(g) P4(s) + 6H2(g)  4PH3(g) 0.42 L H2 x 1
#18 Phosphorus and hydrogen can be combined to form
phosphine (PH3)
P4(s) H2(g)  4PH3(g)
How many liters of phosphine are formed when 0.42 L of
hydrogen reacts with phosphorus?
P4(s) H2(g)  4PH3(g)
? L PH3
0.42 L H2
0.42 L H2 x 1
1 mole H2 x
22.4 L H2
4 moles PH3 x
6 moles H2
22.4 L PH3
1 mole PH2
= 0.28 L PH3

5. CS2 + 3O2  CO2 + 2SO2 27.9 mL O2 x 1 1 L O2 x 1000 mL O2 1 mole O2 x
#19 Consider this equation:
CS O2  CO SO2
27.9 mL O2
? L SO2
(the only trick here is to convert to liters from mL and the
rest of the problem is the same)
27.9 mL O2 x 1
1 L O x
1000 mL O2
1 mole O2 x
22.4 L O2
= L SO2
18.6 mL SO2
2 moles SO2 x
3 moles O2
22.4 L SO2
1mole SO2

6. CS2 + 3O2  CO2 + 2SO2 0.38 L SO2 x 1 1mole SO2 x 22.4 L SO2
#20 Consider this equation:
CS O2  CO SO2
? dL CO2
0.38 L SO2
(the only trick here is to convert to deciliters from Liters)
1 dL is 100 ml or 1/10 of a liter
0.38 L SO2 x 1
1mole SO x
22.4 L SO2
1 mole CO2 x
2 moles SO2
= 1.9 dL CO2
.19 L CO2
22.4 L CO2 x
1 moles CO2
10 dL CO2
1 L CO2