#15 How many molecules of oxygen are produced by the decomposition
of 6.54 g of potassium chlorate
2KClO3 2KCl
6.54 g KClO3 (given)
6.54 g KClO3
1
x
X
1 mole KClO3 X
122.55 g KClO3
6.02 x 1023 molecules O2
1 mole O2
16 +16 +16+ 35.45 + 39.1 = 122.55
molar mass of KClO3
+
3O2
? molecules produced
3 moles O2
2 mole KClO3
= 4.82 x 1022 molecules O2
#16 The last step in the production of nitric acid is the reaction of
nitrogen dioxide with water.
3NO2 + H2O ? g NO2
2HNO3
+ NO
5.00 x 1022 molecules NO (given)
5.00 x 1022 molecules NO x
1 mole NO
x
1
6.02 x 1023 molecules NO
3 moles NO2 x
1 mole NO
16 +16 +14 = 46
molar mass of KClO3
46 g NO2
1 mole NO2
= 11.5 g NO2
#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 3.86 L CO
2CO2
? L O2
3.86 L CO x 1 mole CO x 1 mole O2 x 22.4 L O2
22.4 L CO
2 mole CO
1 mole O2
1
= 1.93 L O2
#18 Phosphorus and hydrogen can be combined to form
phosphine (PH3)
P4(s) +
6H2(g) 4PH3(g)
How many liters of phosphine are formed when 0.42 L of
hydrogen reacts with phosphorus?
P4(s) +
6H2(g) 4PH3(g)
? L PH3
0.42 L H2
0.42 L H2
1
x
1 mole H2
22.4 L H2
22.4 L PH3
1 mole PH2
x
4 moles PH3
6 moles H2
= 0.28 L PH3
x
#19 Consider this equation:
CS2
+
3O2 CO2 + 2SO2
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
1
x
2 moles SO2
3 moles O2
1 L O2
x 1 mole O2 x
1000 mL O2
22.4 L O2
x
22.4 L SO2
1mole SO2
= .018 L SO2
18.6 mL SO2
#20 Consider this equation:
CS2
+
3O2 CO2 + 2SO2
? 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
1
x
22.4 L CO2 x
1 moles CO2
1mole SO2
22.4 L SO2
10 dL CO2
1 L CO2
x
1 mole CO2 x
2 moles SO2
= 1.9 dL CO2
.19 L CO2