TIER 6
Combine the knowledge of gases and solutions to perform stoichiometric calculations
Gas Stoichiometry
Sample Problem
Propane, C3H8, is a gas that is sometimes used as a fuel
for cooking and heating. The complete combustion of
propane occurs according to the following balanced
equation.

C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
(a) What will be the volume, in liters, of oxygen required
for the complete combustion of 0.350 L of propane?
(b) What will be the volume of carbon dioxide produced
in the reaction? Assume that all volume measurements
are made at the same temperature and pressure.
Gas Stoichiometry: VOLUME TO VOLUME
 Sample Problem Solution
 Given: balanced chemical equation;
V of propane = 0.350 L
 Unknown: V of O2
 Solution: Because all volumes are to be compared at
the same conditions, volume ratios can be used like
mole ratios.
.350L C3H8 X 3L CO2 = 1.05 L CO2
1 L C3H8
Gas Stoichiometry:VOLUME TO MASS
Sample Problem
Calcium carbonate, CaCO3, also know as limestone,
can be heated to produce calcium oxide (lime) and
industrial chemical with a wide variety of uses.
CaCO3 (s)  CaO (s) + CO2(g)
How many grams of calcium carbonate must be
decomposed to produce 5.00L of carbon dioxide gas at
STP?
Sample Problem Solution
Given: - Balanced chemical equation;
CaCO3 (s)  CaO (s) + CO2(g)
-V of carbon dioxide= 5.00 L
-STP conditions
Unknown: g of CaCO3
At STP 1 mole of gas occupies 22.4 L
5.00L x 1 mole CO2 = .223 moles CO2
22.4 L
.223 moles CO2 x 1 mole CaCO3 =.223 moles CaCO3
1mole CO2
PROBLEM: How many liters of H2 gas at STP can be produced by
the reaction of 4.6 g Na and excess water according to the
following equation?
2Na(s) + 2 H2O(l)  H2(g) + 2 NaOH (aq)
Sample Problem: MASS TO VOLUME
Tungsten is produced by the reaction of
tungsten oxide with hydrogen.
WO3 (s) + 3H2 (g)  W(s) + 3 H2O(l)
How many liter of hydrogen gas at 35oC and
.980 atm are needed to react completely with
875 g of tungsten oxide?
Sample Problem Solution
Sample Problem Solution
Given: balanced chemical equation
WO3 (s) + 3H2 (g)  W(s) + 3 H2O(l)
-P is .980 atm
-T is 35oC
-mass of WO3
Unknown: V of hydrogen gas
875 g WO3 x
3 mol H2 = 11.3 mole H2
231.84 g WO3
V = nRT = (11.3 mol)(.0821) (308K) = 292L H2
P
.980
PROBLEM: How many liters of gaseous carbon monoxide at 27oC ad
.247 atm can be produced from the burning of 65.5g of carbon
according to the following equation?
2C(s) + O2(g)  2CO(g)
SOLUTION
STOICHIOMETRY
SAMPLE PROBLEM:
In a recent lab, a 2M hydrochloric acid was reacted with 2.00 g
of Magnesium.
Mg(s) + 2HCl  MgCl2 (ag) + H2 (g)
(a)How many cm3 of hydrochloric acid would be needed to
react all the magnesium with out any acid excess.
(b) How many dm3 of hydrogen gas could be produced at STP
SAMPLE PROBLEM SOLUTION
GIVEN: Balanced equation: Mg(s) + 2HCl  MgCl2 (ag) + H2 (g)
-mass of Mg =2.00g
-Molarity of HCl = 2mol dm-3
-STP conditions
UNKNOWN: (a) V of HCl solution
(b) V of H2 gas
(a) 2.00g Mg x 1mole Mg x 2 mole HCl x 1 dm3 HCl = .08 dm3 = 80 cm3
24.31g Mg 1 mole Mg
2 mol HCl
(b) 2.00g Mg x 1 mole Mg x 1 mole H2 x
24.31 g Mg 1 mole Mg
22.4 dm3 = 1.84 dm3
1mole
PROBLEM: In a recent lab, a 3M nitric acid was reacted with 3.50
g of zinc.
Zn(s) + 2HNO3  Zn(NO3 )2(ag) + H2 (g)
(a)How many cm3 of nitric acid would be needed to react all the
zinc with out any acid excess.
(b) How many dm3 of hydrogen gas could be produced at STP