Problem Set Chapter 5
Basic
1. What is the pressure in mm Hg exerted by 2.40 grams of O2 if the volume is 1400 mL and the temperature is 27 oC?
2. What must the final temperature be (in oC) if 600 mL of hydrogen at 125 oC is to be cooled so that its volume is 275 mL with no pressure change?
3. A steel cylinder holds 1.50 grams of ethanol, C2H5OH. What is the pressure of the ethanol vapor if the cylinder has a volume of 251 cm3 and the temperature is 250 oC? (Assume all the ethanol is in the vapor phase at this temperature.)
4. What is the total pressure in atmospheres of a gas mixture that contains1.0 g H2 and 8.0 g of Ar in a 3.0 L container at 27 oC? What are the partial pressures of the two gases?
Involved
1. Boron hydride reacts with oxygen in the following way
2B4H10(g) + 11O2(g) à 4B2O3(s) + 10H2O(g)
If a 0.50 gram sample of boron hydride reacts with excess oxygen, what will be the pressure of gaseous water in a 4.25 liter flask at 30.0 oC?
2. An adult exhales about 15 times per minute, with each exhalation having a volume of
500 . mL. Assuming the inhaled air has no water, but the exhaled air is water vapor at 37.0 oC, what mass of water is lost from the body in one day? The vapor pressure of water at 37.0 oC is 47.1 Torr. Use the molar mass of water.
3. Explosions occur when a substance decomposes rapidly with the production of a large
volume of gases. When detonated, TNT decomposes according to the equation:
2C7H5(NO2)3(s) à 12CO(g) + 2C(s) + 5H2(g) + 3N2(g)
What is the total volume of gases produced from 1.00 kg of TNT if collected at 25.00 oC and 1.00 atm?
4. Benzene is burned according to the following reaction:
2C6H6(l) + 15O2(g) à 12CO2(g) + 6H2O(l)
The percent yield of this reaction is 85.2%. After the reaction is complete, 16.77 L of CO2 is collected at a pressure of 100. kPa and 35.0 oC. How many grams of C6H6(l) were burned?
5. A sample of KClO3 was heated to decompose it to potassium chloride and oxygen. The O2 was collected over water at 21 oC and a barometric pressure of 746 mm Hg. A 155-mL volume of the gaseous mixture was obtained. What mass of KClO3 was decomposed?
Challenging
1. Alkaline earth metal carbonates are decomposed to the metal oxide and CO2 on heating:
MCO3(s) à MO(s) + CO2(g)
You heat 0.158 g of a white, solid carbonate of an alkaline earth metal (M) and find that the evolved CO2 has a pressure of 69.8 mm Hg in a 285-mL flask at 25 oC. Identify M.
2. A compound contains 52% N, 40% B, and 8% H. A sample of the vapor with a
mass of 210 mg occupies a volume of 84.5 mL at 600 mm Hg and 27 oC. What is the molar mass of the compound and its molecular formula?