Chemistry
Unit: Stoichiometry
Name: _____________________________ Date: ______________MOD: _________
Stoichiometric Calculations
Directions: Use stoichiometry and dimensional analysis to problem solve. Be sure to pay
attention to significant figures and include units.
Sample problem: Calculate the number of grams of NH3 produced by the reaction of 5.40 g
of hydrogen with an excess of nitrogen. The balanced equation is:
N2 (g) + 3 H2 (g) → 2 NH3 (g)
Knowns:
Mass of hydrogen = 5.40 g H2
3 mol H2 = 2 mol NH3
1 mol H2 = 2.0 g H2 (molar mass)
1 mol NH3 = 17.0 g NH3 (molar mass)
Unknown:
Mass of ammonia = ________g NH3
Analyze: g H2 → g NH3
o ____ moles H2 react with ___ mol N2 to produce ____ mol NH3
o The following calculations need to be done:
o g _____ → mol ______ → mol _________ → g ________
Calculate
o 1st Convert the given (5.40g H2) into moles
o 2nd Calculate the mol of NH3 from the mol of H2
o 3rd Convert moles of NH3 into grams of NH3
Answer =
o Series of calculations:
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Chemistry
Unit: Stoichiometry
1. The complete combustion of ethanol produces carbon dioxide and water according
to the following chemical equation:
C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)
a) How many moles of oxygen are necessary to produce 18.0 moles of carbon
dioxide?
b) How many grams of carbon dioxide are produced when 1.2 moles of water are
produced?
2. Iron(III) oxide can be decomposed in the presence of hydrogen gas and heat to
produce free iron and water according to the following chemical equation:
Fe2O3(s) + 3H2(g) → 2Fe(s) + 3H2O(g)
a) How many moles of hydrogen gas are needed to produce 90.0 grams of iron?
b) What is the mass of iron produced when 450 grams of iron(III) oxide
decomposes?
3. Dintirogen pentoxide is formed from the combination of nitric acid and oxygen
according to the following chemical equation:
4NO(g) + 3O2(g) → 2N2O5(g)
a) How many liters of oxygen are consumed when 18.0 moles of nitric acid are
available for the reaction?
b) What is the mass of dinitrogen pentoxide produced from 7.00 moles of oxygen?
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