Download Problem Set: Empirical and Molecular Formulas

NPHS / ChemH
Problem Set: Limiting Reactant and Percent Yield
1. Carbon monoxide can be combined with hydrogen to produce methanol, CH 3OH. If you
had 152.5 g CO and 24.50 g H2, how many kilograms of CH3OH would be produced? (Hint:
make sure equation is balanced first!)
CO
+
2H2

CH3OH
152.5 gCO
1molCO
1molCH 3OH 32.0 gCH 3OH



 174.3gCH 3OH
28.0 gCO
1molCO
1molCH 3OH
24.50 gH 2

1molH 2 1molCH 3OH 32.0 gCH 3OH


 196.0CH 3OH
2.0 gH 2
2molH 2
1molCH 3OH
CO is limiting
0.1743Kg CH 3OH will be produced
2. The hydrochloric acid, HCl, secreted in your stomach can be neutralized by taking an
antacid like aluminum hydroxide, Al(OH) 3. If 34.0 g HCl are secreted and 12.0 g Al(OH) 3
are taken, is there enough Al(OH) 3 to react with all of the HCl? (balance eq. first)
3HCl +
Al(OH) 3

AlCl3 +
3H2O
34.0 gHCl
1molHCl
1molAl (OH )3 78.0 gAl (OH )3



 24.2 gAl (OH )3
36.5 gHCl
3molHCl
1molAl (OH )3
34.0g HCl needs 24.2 g Al(OH)3 to react completely, 12.0g Al(OH)3 is not enough
3. Ammonia, NH3, is used throughout the world as a fertilizer. To manufacture ammonia,
nitrogen, N2, is combined with hydrogen, H2, in a synthesis reaction.
a) Write a balanced chemical equation for the formation of ammonia.
b) If 92.7 kg N2 and 265.8 kg H2 are used, which is the limiting reactant?
4. Using the same reaction for the production of ammonia as in #3, determine the percent
yield when 400.0 kg of H2 are added to an excess of N2, and 1040. kg of NH3 are produced.
5. A standard laboratory preparation of iodine is the following reaction:
NaI + MnO2 + H2SO4  Na2SO4 + MnSO4 + H2O + I2
When 62.55 g of NaI are used with excess amounts of the other reactants, the actual yield
of iodine (I2) was 39.78 g. What is the percent yield?
6. Titanium (IV) oxide, TiO2, is used as a pigment in paints and as a whitening and coating
agent for paper. It can be made by reacting O2 with TiCl4.
TiCl4 + O2  TiO2 + 2 Cl2 (already balanced)
a) If 4.5 mol of TiCl4 react with 3.5 mol O2, identify both the limiting and excess
reactants.
b) How many moles of excess reactant will remain if the reaction goes to
completion?
c) How many moles of each product should be formed if the reaction goes to
completion?
7. How much nitric acid, HNO3, is produced when NO2 gas is bubbled under pressure
through 100.0 g of H2O? (Assume the reaction goes to completion)
3NO2 + H2O  2HNO3 + NO (already balanced)
8. When phosphorus burns in the presence of oxygen, P4O10 is produced. In turn, P4O10
reacts with water to produce phosphoric acid, which is one of the compounds found in acid
precipitation.
P4O10 + H2O  H3PO4
a) Write a balanced equation for this reaction.
b) When 100.0 g of P4O10 are reacted with 200.0 g of H2O, what is the
theoretical yield of phosphoric acid?
c) If the actual yield is 126.24 g of H3PO4, what is the percent yield for this
reaction?
9. Coal gasification is a process that converts coal into methane gas. If this reaction has a
percent yield of 85.0%, how much methane can be obtained from 1250 g of carbon?
2C + 2H2O  CH4 + CO2
10. If the percent yield for the coal gasification process in problem #9 can be increased to
95.0%, how much methane can be obtained from 2750 g of carbon?