Gases

According to the kinetic-molecular theory, the _______ of a gas is a measurement of the average kinetic energy of its molecules.

absolute temperature

Charles's law applies to a fixed amount of gas at constant pressure. The law states that the volume of the gas is directly proportional to its...

absolute temperature, as measured on the Kelvin scale.

Charles's law explains the relationship between the volume of a gas and its absolute temperature. Under which of these conditions does Charles's law LEAST apply to the changing volume of a gas?

at temperatures near absolute zero

The diagram above shows a mercury barometer, in which a column of mercury of height h has risen up a thin glass tube. When converted to the proper units, what pressure does the height h represent?

atmospheric pressure

Which of these conditions describe the IUPAC standard temperature and pressure (STP)?

0° Celsius and 1 atmosphere

A 350 mL sample of gas is held at 1.0 atm of pressure and a temperature of 25°C. How many moles of the gas are present? (Note: The gas constant is 0.0821 L-atm/mol-K.)

0.014 mol

A chemist fills a sealed container with 4.5 mol of Gas X and 5.5 mol of Gas Y. No other gases are in the container. If the pressure inside the container is 1.8 atmospheres, what is the partial pressure of Gas X?

0.81 atmosphere

A piston with a freely movable top has a valve through which gases can enter and leave. In one procedure, the piston is filled with 4.5 mol of carbon dioxide gas (CO2). The piston is then compressed to one third its size, forcing much of the gas out the valve. How much carbon dioxide remains in the piston? (Assume the procedure does not change the pressure and temperature of the carbon dioxide inside the piston.)

1.5 mol

A sample of gas in a 2.0-L container has a temperature of 50° Celsius. If the temperature is raised to 100° Celsius and the pressure of the container is held constant, what will be the new volume of the gas?

2.3 L

A 4.0-L sample of gas is held at a pressure of 760 torr. What will be the new volume of the gas when the pressure is raised to 1140 torr at constant temperature?

2.7 L

The following samples of gases are each kept at the same temperature and pressure. Which sample has the greatest volume?

4 mol of neon (Ne)

Balloon N is filled with nitrogen gas (N2), while Balloon H is filled with hydrogen gas (H2). Both balloons are filled to the same volume at the same pressure and temperature, and both are made of the same material. Over time, gases leak out of both balloons through tiny holes in their material. Which balloon shrinks faster, and why?

Balloon H shrinks faster because hydrogen gas has the smaller molecular weight.

Earth's atmosphere is approximately 78% nitrogen gas by volume. Which of these values, if any, equals 0.78? I. the partial pressure of nitrogen at sea level, expressed in units of atmospheres (atm) II. the mole fraction of nitrogen in Earth's atmosphere III. the gas constant (R) for nitrogen in Earth's atmosphere

I and II only

A scientist is very precisely measuring the volumes of 1.00-mol samples of chlorine gas, methane gas, and helium gas, each at standard temperature and pressure. What statements describe the three volumes she measures? I. The volume of each gas is very close to the same value. II. The mass of each gas is very close to the same value. III. The three gases have slightly different volumes when measured with enough precision.

I and III only

Pressure is commonly measured by many units, among them.... I. atmospheres (atm) II. torr III. millimeters of mercury (mm Hg)

I, II, and III

The ideal gas equation is a consequence of which laws about the behavior of gases? I. Boyle's law II. Charles' law III. Avogadro's law

I, II, and III

The kinetic-molecular theory of gases includes which of these principles? I. Gases consist of tiny particles that are in constant, random motion. II. The total volume of individual gas particles is negligibly small. III. Individual gas particles neither attract nor repel one another significantly.

I, II, and III

Graham's law relates the rates of effusion of two gases to their molar masses. To which of these situations can Graham's law be reasonably applied? I. Air moves in and out of the lungs when the chest expands and contracts. II. A mixture of two gases leaks out of a container through a pinhole-sized opening. III. Containers of two gases are opened at opposite ends of the room, and the gases spread throughout the room.

II and III only

Chlorine gas is pumped at high pressure into a piston with a movable top. Then, over a long period of time, both the pressure inside the piston and its volume become lower, while the temperature remains the same. Which of these events, if any, could explain this result? (Assume that gas is not leaking out of the piston and that the measurements of pressure and volume are accurate.) I. Chlorine gas is behaving as a real gas, not an ideal gas. II. Some of the chlorine gas is reacting with the lining of the piston to form a solid tarnish. III. Some of the chlorine gas is reacting with the lining of the piston to form another gas.

II only

Which of the following activities best demonstrates Boyle's law? I. placing an air-filled balloon in a freezer II. inflating a balloon with air III. breathing air in and out of your lungs

III only

The three most common gases in Earth's atmosphere are nitrogen (N2), oxygen (O2), and Argon (Ar). A scientist seals a flask with a sample of the atmosphere at a pressure of 1.0 atm, and then raises its temperature from 20ºC to 80ºC. Which of these data, if any, does the scientist need to accurately predict the new pressure inside the flask? I. the partial pressures of each component gas II. the relative volumes of each component gas III. the volume of one particle (either atom or molecule) of each component gas

None of these data are needed.

A sealed 5.0-L glass container is filled with equal amounts of nitrogen gas (N2) and hydrogen gas (H2) at 1.0 atm of pressure. The volume of the container is then reduced to 2.5 L under conditions of constant temperature. The pressure, however, increases to a pressure that is significantly less than 2.0 atm, which is what Boyle's law predicts. What is the most likely explanation for this observation?

Some of the nitrogen and hydrogen reacted to form ammonia (NH3).

According to Boyle's law, the volume of a fixed amount of gas is inversely proportional to its pressure only when which of these conditions is true?

The temperature of the gas remains constant.

Which of the following is a unit of pressure?

newton per meter squared (N/m2)

In the van der Waals equation for gases, two constants are included to correct for the non-ideal behavior of real gases. What two factors do these constants correct for?

the volume of gas molecules and their molecular attraction