Chemistry
Name:________________________
Stoichiometry Practice #2
1.
Date:__________________
One in a series of reactions that inflate airbags in automobiles is the decomposition of
sodium azide (NaN3). Determine the mass of nitrogen produced if 100.0 g of NaN3 is
decomposed. (reaction is unbalanced)
NaN3(s) →
Na(s) +
N2(g)
2. In the formation of acid rain, sulfur dioxide from pollution reacts with oxygen and water in
the air to form sulfuric acid (H2SO4).
A. Write the balanced chemical equation for the reaction.
B. If 2.50 g of SO2 reacts with excess oxygen and water, how many grams of H2SO4 are
produced?
3. Chloroform (CHCl3), an important solvent, is produced by a reaction between methane and
chlorine. How many grams of CH4 are needed to produce 50.0 g CHCl3? (reaction is
unbalanced)
CH4(g) +
Cl2(g) →
CHCl3(g) +
HCl(g)
4. Gasohol is a mixture of ethanol and gasoline. Balance the equation and determine the mass
of CO2 produced from the combustion of 100.0 g of ethanol.
C2H5OH(l) +
O2(g) → CO2(g) +
H2O(g)
5. When surface water dissolves carbon dioxide, carbonic acid (H2CO3) is formed. When the
water moves underground through limestone formations, the limestone dissolves and caves
are sometimes produced. What mass of limestone must have dissolved if 3.05 x 10 5 kg of
calcium hydrogen carbonate was produced?
CaCO3(s) +
H2CO3(aq) →
Ca(HCO3)2(aq)
6. To extract gold from its ore, the ore (represented here as Au), is treated with a sodium
cyanide solution in the presence of oxygen and water.
A. Determine the mass of gold that can be extracted if 25.0 g of sodium cyanide is used?
B. If the mass of the ore from which the gold was extracted is 150.0 g, what percentage
of the ore is gold?
4Au(s) + 8NaCN(aq) + O2(g) + 2H2O(l) → 4NaAu(CN)2(aq) + 4NaOH(aq)