Chapter 5

Name five elements and five compounds that exist as gases at room temperature.

List the physical characteristics of gases.

Define pressure and give the common units for pressure.

When you are in a plane flying at high altitudes, your ears often experience pain. This discomfort can be temporarily relieved by yawning or swallowing some water. Explain.

Why is mercury a more suitable substance to use in a barometer than water?

Explain how a unit of length (mmHg) can be used as a unit for pressure.

What is the difference between a gas and a vapor? At \(25^{\circ} \mathrm{C},\) which of the following substances in the gas phase should be properly called a gas and which should be called a vapor: molecular nitrogen \(\left(\mathrm{N}_{2}\right)\), mercury?

If the maximum distance that water may be brought up a well by a suction pump is \(34 \mathrm{ft}(10.3 \mathrm{~m})\), how is it possible to obtain water and oil from hundreds of feet below the surface of Earth?

Why is it that if the barometer reading falls in one part of the world, it must rise somewhere else?

Why do astronauts have to wear protective suits when they are on the surface of the moon?

Convert \(562 \mathrm{mmHg}\) to atm.

The atmospheric pressure at the summit of Denali (formerly known as Mt. McKinley) is \(606 \mathrm{mmHg}\) on a certain day. What is the pressure in atm and in kPa?

State the following gas laws in words and also in the form of an equation: Boyle's law, Charles' law, Avogadro's law. In each case, indicate the conditions under which the law is applicable, and give the units for each quantity in the equation.

A gas occupying a volume of \(725 \mathrm{~mL}\) at a pressure of 0.970 atm is allowed to expand at constant temperature until its pressure reaches 0.541 atm. What is its final volume?

A gas occupying a volume of \(725 \mathrm{~mL}\) at a pressure of 0.970 atm is allowed to expand at constant temperature until its pressure reaches 0.541 atm. What is its final volume?

The volume of a gas is \(5.80 \mathrm{~L}\), measured at 1.00 atm. What is the pressure of the gas in \(\mathrm{mmHg}\) if the volume is changed to \(9.65 \mathrm{~L} ?\) (The temperature remains constant.)

A sample of air occupies \(3.8 \mathrm{~L}\) when the pressure is 1.2 atm. (a) What volume does it occupy at 6.6 atm? (b) What pressure is required in order to compress it to \(0.075 \mathrm{~L} ?\) (The temperature is kept constant.)

A 36.4-L volume of methane gas is heated from \(25^{\circ} \mathrm{C}\) to \(88^{\circ} \mathrm{C}\) at constant pressure. What is the final volume of the gas?

Under constant-pressure conditions a sample of hydrogen gas initially at \(88^{\circ} \mathrm{C}\) and \(9.6 \mathrm{~L}\) is cooled until its final volume is \(3.4 \mathrm{~L}\). What is its final temperature?

Ammonia burns in oxygen gas to form nitric oxide (NO) and water vapor. How many volumes of NO are obtained from one volume of ammonia at the same temperature and pressure?

Molecular chlorine and molecular fluorine combine to form a gaseous product. Under the same conditions of temperature and pressure it is found that one volume of \(\mathrm{Cl}_{2}\) reacts with three volumes of \(\mathrm{F}_{2}\) to yield two volumes of the product. What is the formula of the product?

List the characteristics of an ideal gas. Write the ideal gas equation and also state it in words. Give the units for each term in the equation.

What are standard temperature and pressure (STP)? What is the significance of STP in relation to the volume of 1 mole of an ideal gas?

Why is the density of a gas much lower than that of a liquid or solid under atmospheric conditions? What units are normally used to express the density of gases?

A sample of nitrogen gas kept in a container of volume \(2.3 \mathrm{~L}\) and at a temperature of \(32^{\circ} \mathrm{C}\) exerts a pressure of 4.7 atm. Calculate the number of moles of gas present.

A certain amount of gas at \(25^{\circ} \mathrm{C}\) and at a pressure of 0.800 atm is contained in a glass vessel. Suppose that the vessel can withstand a pressure of 2.00 atm. How high can you raise the temperature of the gas without bursting the vessel?

A gas-filled balloon having a volume of \(2.50 \mathrm{~L}\) at 1.2 atm and \(25^{\circ} \mathrm{C}\) is allowed to rise to the stratosphere (about \(30 \mathrm{~km}\) above the surface of Earth), where the temperature and pressure are \(-23^{\circ} \mathrm{C}\) and \(3.00 \times 10^{-3}\) atm, respectively. Calculate the final volume of the balloon.

The temperature of \(2.5 \mathrm{~L}\) of a gas initially at \(\mathrm{STP}\) is raised to \(250^{\circ} \mathrm{C}\) at constant volume. Calculate the final pressure of the gas in atm.

The pressure of \(6.0 \mathrm{~L}\) of an ideal gas in a flexible container is decreased to one-third of its original pressure, and its absolute temperature is decreased by one-half. What is the final volume of the gas?

A gas evolved during the fermentation of glucose (wine making) has a volume of \(0.78 \mathrm{~L}\) at \(20.1^{\circ} \mathrm{C}\) and 1.00 atm. What was the volume of this gas at the fermentation temperature of \(36.5^{\circ} \mathrm{C}\) and \(1.00 \mathrm{~atm}\) pressure?

Calculate its volume (in liters) of \(88.4 \mathrm{~g}\) of \(\mathrm{CO}_{2}\) at STP.

A gas at \(772 \mathrm{mmHg}\) and \(35.0^{\circ} \mathrm{C}\) occupies a volume of \(6.85 \mathrm{~L}\). Calculate its volume at STP.

At STP, \(0.280 \mathrm{~L}\) of a gas weighs \(0.400 \mathrm{~g}\). Calculate the molar mass of the gas.

At 741 torr and \(44^{\circ} \mathrm{C}, 7.10 \mathrm{~g}\) of a gas occupy a volume of \(5.40 \mathrm{~L}\). What is the molar mass of the gas?

Ozone molecules in the stratosphere absorb much of the harmful radiation from the sun. Typically, the temperature and pressure of ozone in the stratosphere are \(250 \mathrm{~K}\) and \(1.0 \times 10^{-3}\) atm, respectively. How many ozone molecules are present in \(1.0 \mathrm{~L}\) of air under these conditions?

Assuming that air contains 78 percent \(\mathrm{N}_{2}, 21\) percent \(\mathrm{O}_{2}\), and 1 percent Ar, all by volume, how many molecules of each type of gas are present in \(1.0 \mathrm{~L}\) of air at STP?

A 2.10-L vessel contains 4.65 g of a gas at 1.00 atm and \(27.0^{\circ} \mathrm{C}\). (a) Calculate the density of the gas in grams per liter. (b) What is the molar mass of the gas?

Calculate the density of hydrogen bromide (HBr) gas in grams per liter at \(733 \mathrm{mmHg}\) and \(46^{\circ} \mathrm{C}\).

A certain anesthetic contains 64.9 percent \(\mathrm{C}, 13.5\) percent \(\mathrm{H},\) and 21.6 percent \(\mathrm{O}\) by mass. At \(120^{\circ} \mathrm{C}\) and \(750 \mathrm{mmHg}, 1.00 \mathrm{~L}\) of the gaseous compound weighs \(2.30 \mathrm{~g}\). What is the molecular formula of the compound?

A compound has the empirical formula \(\mathrm{SF}_{4}\). At \(20^{\circ} \mathrm{C}, 0.100 \mathrm{~g}\) of the gaseous compound occupies a volume of \(22.1 \mathrm{~mL}\) and exerts a pressure of 1.02 atm. What is the molecular formula of the gas?

What pressure will be required for neon at \(30^{\circ} \mathrm{C}\) to have the same density as nitrogen at \(20^{\circ} \mathrm{C}\) and \(1.0 \mathrm{~atm} ?\)

The density of a mixture of fluorine and chlorine gases is \(1.77 \mathrm{~g} / \mathrm{L}\) at \(14^{\circ} \mathrm{C}\) and 0.893 atm. Calculate the mass percent of the gases.

Consider the formation of nitrogen dioxide from nitric oxide and oxygen: $$ 2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}_{2}(g) $$ If \(9.0 \mathrm{~L}\) of \(\mathrm{NO}\) are reacted with excess \(\mathrm{O}_{2}\) at \(\mathrm{STP}\), what is the volume in liters of the \(\mathrm{NO}_{2}\) produced?

In alcohol fermentation, yeast converts glucose to ethanol and carbon dioxide: $$ \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s) \longrightarrow 2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+2 \mathrm{CO}_{2}(g) $$ If \(5.97 \mathrm{~g}\) of glucose are reacted and \(1.44 \mathrm{~L}\) of \(\mathrm{CO}_{2}\) gas are collected at \(293 \mathrm{~K}\) and \(0.984 \mathrm{~atm},\) what is the percent yield of the reaction?

A compound of \(\mathrm{P}\) and \(\mathrm{F}\) was analyzed as follows: Heating \(0.2324 \mathrm{~g}\) of the compound in a \(378-\mathrm{cm}^{3}\) container turned all of it to gas, which had a pressure of \(97.3 \mathrm{mmHg}\) at \(77^{\circ} \mathrm{C}\). Then the gas was mixed with calcium chloride solution, which turned all of the \(\mathrm{F}\) to \(0.2631 \mathrm{~g}\) of \(\mathrm{CaF}_{2}\). Determine the molecular formula of the compound.

A quantity of \(0.225 \mathrm{~g}\) of a metal \(\mathrm{M}\) (molar mass = \(27.0 \mathrm{~g} / \mathrm{mol}\) ) liberated \(0.303 \mathrm{~L}\) of molecular hydrogen (measured at \(17^{\circ} \mathrm{C}\) and \(741 \mathrm{mmHg}\) ) from an excess of hydrochloric acid. Deduce from these data the corresponding equation and write formulas for the oxide and sulfate of M.

Dissolving \(3.00 \mathrm{~g}\) of an impure sample of calcium carbonate in hydrochloric acid produced \(0.656 \mathrm{~L}\) of carbon dioxide (measured at \(20.0^{\circ} \mathrm{C}\) and \(792 \mathrm{mmHg}\) ). Calculate the percent by mass of calcium carbonate in the sample. State any assumptions.

Calculate the mass in grams of hydrogen chloride produced when \(5.6 \mathrm{~L}\) of molecular hydrogen measured at STP react with an excess of molecular chlorine gas.

Ethanol \(\left(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\right)\) burns in air: $$ \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l) $$ Balance the equation and determine the volume of air in liters at \(35.0^{\circ} \mathrm{C}\) and \(790 \mathrm{mmHg}\) required to burn \(227 \mathrm{~g}\) of ethanol. Assume that air is 21.0 percent \(\mathrm{O}_{2}\) by volume.

(a) What volumes (in liters) of ammonia and oxygen must react to form \(12.8 \mathrm{~L}\) of nitric oxide according to the equation at the same temperature and pressure? $$ 4 \mathrm{NH}_{3}(g)+5 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{NO}(g)+6 \mathrm{H}_{2} \mathrm{O}(g) $$ (b) What volumes (in liters) of propane and water vapor must react to form \(8.96 \mathrm{~L}\) of hydrogen according to the equation at the same temperature and pressure? $$ \mathrm{C}_{3} \mathrm{H}_{8}(g)+3 \mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 3 \mathrm{CO}(g)+7 \mathrm{H}_{2}(g) $$