7. Gases

Calculate the average molecular weight of air from the data given in Table 10.1.

During a person's typical breathing cycle, the CO2 concentration in the expired air rises to a peak of 4.6% by volume. (a) Calculate the partial pressure of the CO2 in the expired air at its peak, assuming 1 atm pressure and a body temperature of 37 °C.

The atmospheric concentration of CO2 gas is presently 407 ppm (parts per million, by volume; that is, 407 L of every 106 L of the atmosphere are CO2). What is the mole fraction of CO2 in the atmosphere?

What is the mole fraction of oxygen gas in air (see Table 5.3)? What volume of air contains 10.0 g of oxygen gas at 273 K and 1.00 atm?

(a) What are the mole fractions of O2 in a mixture of 15.08 g of O2, 8.17 g of N2, and 2.64 g of H2?

(a) What are the mole fractions of H2 in a mixture of 15.08 g of O2, 8.17 g of N2, and 2.64 g of H2?

(a) What are the mole fractions of N2 in a mixture of 15.08 g of O2, 8.17 g of N2, and 2.64 g of H2?

What is the mole fraction of each gas in the mixture described in Problem 10.83?

Fluorocarbons (compounds that contain both carbon and fluorine) were, until recently, used as refrigerants. The compounds listed in the following table are all gases at 25 °C, and their solubilities in water at 25 °C and 1 atm fluorocarbon pressure are given as mass percentages. (c) Infants born with severe respiratory problems are sometimes given liquid ventilation: They breathe a liquid that can dissolve more oxygen than air can hold. One of these liquids is a fluorinated compound, CF3(CF2)7Br. The solubility of oxygen in this liquid is 66 mL O2 per 100 mL liquid. In contrast, air is 21% oxygen by volume. Calculate the moles of O 2 present in an infant's lungs (volume: 15 mL) if the infant takes a full breath of air compared to taking a full 'breath' of a saturated solution of O 2 in the fluorinated liquid. Assume a pressure of 1 atm in the lungs. Fluorocarbon Solubility (mass %) CF4 0.0015 CClF3 0.009 CCl2F2 0.028 CHClF2 0.30

A gaseous fuel mixture stored at 745 mmHg and 298 K contains only methane (CH4) and propane (C3H8). When 11.7 L of this fuel mixture is burned, it produces 769 kJ of heat. What is the mole fraction of methane in the mixture? (Assume that the water produced by the combustion is in the gaseous state.)

The percent by volume of oxygen (20.95%) is constant throughout the troposphere. (a) Express this percentage as a mole fraction.

The apparatus shown consists of three temperature-jacketed 1.000-L bulbs connected by stopcocks. Bulb A contains a mixture of H2O1g2, CO21g2, and N21g2 at 25 °C and a total pressure of 564 mm Hg. Bulb B is empty and is held at a temperature of -70 °C. Bulb C is also empty and is held at a temperature of 190 °C. The stopcocks are closed, and the volume of the lines connecting the bulbs is zero. CO2 sublimes at -78 °C, and N2 boils at -196 °C.

(a) The stopcock between A and B is opened, and the system is allowed to come to equilibrium. The pressure in A and B is now 219 mm Hg. What do bulbs A and B contain?