## Gas Laws Practice Questions I

Look at the demo for the reaction between 5 ml of HCl 3M and a small piece of magnesium of unknown mass. After the reaction is complete, 31 ml of water were collected in the graduated cylinder.

Questions 1-5 are related to the experiment in the figure.

1. The Balanced chemical equation for the reaction observed is:
2. The proportionality between the gas formed in the reaction and the volume of water is:
• A) Volume of water is equal to the mass of magnesium used
• B) Volume of water double the volume of gas formed
• C) Volume of water is equal to the volume of gas formed
• D) Volume of water is equal to the volume of magnesium
• E) Volume of water is independent to the volume of gas formed
1. Assuming the volume of water collected is 31.0 ml, temperature of the room is T= 20 °C and the P= 942.4mmHg, The calculated number of moles of magnesium used in the reaction is:

(R=0.082 L atm/ K . mol)

• A) 1.54
• B) 0.154
• C) 0.0054
• D) 1.54 x 10-3
• E) 0.54
1. Assuming the volume of water collected is 31.0 ml, temperature of the room is T= 20 °C and the P= 942.4mmHg, The calculated mass of magnesium used in the reaction is:
• A) 37.45 g
• B) 3.745
• C) 0.131
• D) 0.0377
• E) 0.37
1. How many liters of hydrogen gas at STP will be produced if 12.15 g of magnesium were used instead in the experiment with an excess of hydrochloric acid?
• A) 1.00 L
• B) 2.00 L
• C) 5.60 L
• D) 11.2 L
• E) 22.4 L
1. Gases generally have
• A) low density
• B) high density
• C) closely packed particles
• D) no increase in volume when temperature is increased
• E) no decrease in volume when pressure is increased
1. Real gases are those that
• A) only behave ideally at high pressures or low temperatures
• B) deviate from ideal behavior
• C) are only available naturally in the earth’s atmosphere
• D) are called real gases because their behavior can easily be modeled
• E) have an even number of protons
1. Which of the following effects will make PV/nRT less than one for a real gas?
• A) The gas molecules are large enough to occupy a substantial amount of space.
• B) A large number of molecules have speeds greater than the average speed.
• C) The gas molecules have a very low molar mass.
• D) The gas molecules attract one another.
• E) None of these.
1. Graham’s law states that:
• A) Equal amounts of gases occupy the same volume at constant temperature and pressure.
• B) The volume of a fixed amount of gas is inversely proportional to its pressure at constant temperature.
• C) The volume of a fixed amount of gas is directly proportional to its temperature in Kelvin at constant pressure.
• D) The total pressure of a mixture of gases is the simple sum of the partial pressure of all of the gaseous compounds.
• E) The rates of effusion of gases are inversely proportional to the square roots of their molar masses.
1. A hot-air balloon rises. What is the best explanation for this observation?
• A) The pressure on the walls of the balloon increases with increasing temperature.
• B) The difference in temperature between the air inside and outside the balloon produces convection currents.
• C) The cooler air outside the balloon pushes in on the walls of the balloon.
• D) The rate of diffusion of cooler air is less than that of warmer air.
• E) The density of the air inside the balloon is less than that of the surrounding air.
1. Which of the following is included as a postulate in the kinetic molecular theory of an ideal gas?
• A) The distance between gas molecules is small compared with the size of the molecule.
• B) All collisions between molecules are elastic.
• C) In an average collision between molecules, both molecules have the same kinetic energy.
• D) All molecules move randomly in zigzag directions.
• E) All the molecules have the same velocity.
1. All the following are postulates of the kinetic-molecular theory of gases except:
• A) The collisions between molecules are elastic.
• B) The gas molecules are in constant motion.
• C) At a constant temperature, each molecule has the same kinetic energy.
• D) The volumes of the molecules are negligible compared with the volume of the container.
• E) The gas molecules are in rapid motion.
1. The local weather forecaster reports that the current barometric pressure is 30.4 inches of mercury. What is the current pressure in atmospheres?
• A) 1.02 atm
• B) 10.29 atm
• C) 1.00 atm
• D) 4.05 atm
• E) 910 atm
• A) Equal amounts of gases occupy the same volume at constant temperature and pressure.
• B) The volume of a fixed amount of gas is inversely proportional to its pressure at constant temperature.
• C) The volume of a fixed amount of gas is directly proportional to its temperature in Kelvin at constant pressure.
• D) The total pressure of a mixture of gases is the simple sum of the partial pressure of all of the gaseous compounds.
• E) The rates of effusion of gases are inversely proportional to the square roots of their molar masses.
1. Gaseous chlorine is held in two separate containers at identical temperature and pressure. The volume of container 1 is 1.30 L, and it contains 6.70 mol of the gas. The volume of container 2 is 2.33 L. How many moles of the gas are in container 2?
• A) 12.0 mol
• B) 20.3 mol
• C) 0.452 mol
• D) 3.74 mol
• E) none of these
1. A balloon has a volume of 2.32 liters at 24.0°C. The balloon is heated to 48.0°C. Calculate the new volume of the balloon.
• A) 2.32 L
• B) 2.51 L
• C) 2.15 L
• D) 4.64 L
• E) 1.16 L
1. Body temperature is about 309 K. On a cold day, what volume of air at 276 K must a person with a lung capacity of 2.2 L breathe in to fill the lungs?
• A) 2.46 L
• B) 1.97 L
• C) 2.08 L
• D) 3.93 L
• E) none of the above
1. You have a certain mass of helium gas (He) in a rigid steel container. You add the same mass of neon gas (Ne) to this container. Which of the following best describes what happens? Assume the temperature is constant.
• A) The pressure in the container doubles.
• B) The pressure in the container increases but does not double.
• C) The pressure in the container more than doubles.
• D) The volume of the container doubles.
• E) The volume of the container more than doubles.

1. Which contains the largest number of molecules?
• D) All are the same.
1. In which flask are the molecules least polar and therefore most ideal in behavior?
• D) All are the same.

You have two samples of the same gas in the same size container, with the same pressure. The gas in the first container has a Kelvin temperature four times that of the gas in the other container.

1. The ratio of the number of moles of gas in the first container compared to that in the second is
• A) 1:1
• B) 4:1
• C) 1:4
• D) 2:1
• E) 1:2
1. A gas sample is heated from -20.0°C to 57.0°C and the volume is increased from 2.00 L to 4.50 L. If the initial pressure is 0.140 atm, what is the final pressure?
• A) 0.0477 atm
• B) –0.177 atm
• C) 0.411 atm
• D) 0.242 atm
• E) 0.0811 atm
1. A sample of oxygen gas has a volume of 1.72 L at 27°C and 800.0 torr. How many oxygen molecules does it contain?
• A) 4.43 x 1022
• B) 3.36 x 1025
• C) 4.92 x 1023
• D) 8.19 x 1024
• E) none of the above
1. You fill a balloon with 2.50 moles of gas at 22°C at a pressure of 1.62 atm. What is the volume of the balloon?
• A) 15.7 L
• B) 98.0 L
• C) 37.4 L
• D) 2.79 L
• E) 22.4 L
1. What volume is occupied by 21.0 g of methane (CH4) at 27°C and 1.25 atm?
• A) 37.2 L
• B) 25.8 L
• C) 2.32 L
• D) L
• E) not enough data to calculate