Gas Stoichiometry
Remember that stoichiometry involves using mole ratios to compare the amount of reactants used in a reaction to the amount of products made. Now that we know how the volume of a gas relates to the number of moles, we can solve more types of stoichiometry problems.
Recall the process we used for regular stoichiometry problems. It is shown below, but two boxes have been added to show how to solve problems involving volume.
1. 2. 3. 4.
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You can do limiting factor or % yield problems in the same manner as before.
¨ The following practice problems are organized into three sections of increasing difficulty. Do as many of these as you need in order to feel confident.
¨ The correct answers are given in parentheses after the problem so that you can check your work.
Section 1
1. Consider the formation of nitrogen dioxide from nitric oxide and oxygen:
2NO (g) + O2 (g) à 2NO2 (g)
If 9.0 L of NO are reacted with excess O2 at STP, what is the volume in liters of the NO2 produced? (9.0 L)
2. Methane, CH4, the principal component of natural gas, is used for heating and cooking. Write a balanced equation for its combustion. If 15.0 moles of CH4 are reacted, what is the volume of CO2 (in liters) produced at 23.0˚C and 0.985 atm? ( )
Section 2
3. Ammonium sulfate, (NH4)2SO4, can be prepared by a reaction of ammonia gas, NH3, and sulfuric acid, H2SO4. What volume of NH3 gas measured at 78˚C and a pressure of 1.66 atm will be needed to produce 5000. g of ammonium sulfate. ( )
4. Carbon disulfide burns in oxygen to produce carbon dioxide gas and sulfur dioxide gas. Determine the mass of CS2 required to produce 15.7 L of SO2 gas at 25˚C and 99.4 kPa. ( )
5. How many grams of calcium nitride would be needed to produce 750.0 ml of ammonia at 212 kPa and 300.˚C using the equation Ca3N2 + 6H2O à 3Ca(OH)2 + 2NH3 ? (2.48 g)
6. Oxygen masks for producing O2 in emergency situations contain potassium superoxide, KO2. If 5.15 liters of O2 at 35˚C and 99.5 kPa were wanted, how many grams of KO2 would be needed? The equation is 4KO2 + 2H2O + 4CO2 à 4KHCO3 + 3O2 (19.0 g)
7. The air pollutant nitric oxide, NO, is produced by automobile engines. It forms another pollutant, NO2, by reacting with O2. Determine the mass of NO2 produced if 26.25 liters of NO react at 150.˚C and 115.0 kPa with excess O2. The equation is 2NO + O2 à 2NO2 (39.5g)
8. Silver tarnishes in the presence of hydrogen sulfide and oxygen according to the reaction 4Ag + 2H2S + O2 à 2Ag2S + 2H2O How many liters of O2 at 100.˚C and 115 kPa would be needed to react with 10.00 grams of silver? (0.625 L)
9. The metabolic breakdown of glucose, C6H12O6, in our bodies produces CO2, which is expelled from our lungs as gas:
C6H12O6 (s) + 6 O2 (g) à 6 CO2 (g) + 6 H2O (l)
Calculate the volume of dry CO2 produced at body temperature (37˚C) and 1.00 atm when 5.00 g of glucose is consumed in this reaction.
10. When coal is burned, the sulfur present in coal is converted to sulfur dioxide which is responsible for acid rain: S (s) + O2 (g) à SO2 (g)
If 2.54 kg of S are reacted with oxygen, calculate the volume in milliliters of SO2 gas formed at 30.5˚C and 1.12 atm.
Section 3
11. Ammonia is synthesized from the reaction of hydrogen gas and nitrogen gas: N2 + H2 à NH3 If 5.0 liters of N2 and 7.0 L of H2 react at 21˚C and 100. kPa, how many liters of NH3 would be produced at 25˚C and 103 kPa?
12. In the reaction H2O + Cl2O à 2 HOCl, if 4.00 L of H2O at 5.00˚C and 75 kPa react with 3.00 L of Cl2O at STP, how many grams of HOCl would be produced? (13.9 g)
13. Acetylene, C2H2, which is used as a fuel in welding torches is produced in a reaction between calcium carbide and water: CaC2 + 2H2O à Ca(OH)2 + C2H2 Determine the liters of acetylene produced at STP if 10.50 g CaC2 reacts with 7.50 g H2O. (3.67 L)
14. In alcohol fermentation, yeast converts glucose to ethanol and carbon dioxide:
C6H12O6 (s) à 2 C2H5OH (l) + 2 CO2 (g)
If 5.97 g of glucose are reacted and 1.44 L of CO2 gas are collected at 293 K and 0.984 atm, what is the percent yield of the reaction?