5.1.2 Boyle's Law

Question 1

Boyle’s Law

Answer 1

• Boyle’s law states that for a given amount of gas at constant temperature, the volume is inversely proportional to the pressure.

Question 2

note

Answer 2

• Boyle’s law states that for a given amount of gas at constant temperature, the volume (V) is inversely proportional to the pressure (P). In other words, as the pressure increases, the volume decreases (or vice versa).
• This can be stated mathematically as P 1/V. Rearranging this expression yields P ·V = constant.
• Since the pressure times the volume is constant, the pressure times the volume at an initial condition (Pi ·Vi) will equal the pressure times the volume at a final condition (Pf ·Vf). This relationship can be used to solve for Pi, Vi, Pf, or Vf, given the other three variables.
• Boyle’s law can be used to explain how a stomp rocket works—as the volume decreases in the stomp rocket pump, the pressure increases in the hose, launching the rocket.
• Given an initial volume (Vi), a final volume (Vf), and an initial pressure (Pi), Boyle’s law can be used to solve for the final pressure (Pf).

Question 3

Using Boyle’s Law, predict what will happen to the volume of a gas if there is an increase in pressure. Assume that the temperature and the number of moles of gas remain constant.

Answer 3

The volume will decrease.

Question 4

Suppose that a gas sample in a balloon has a volume of 883 cm3 at a pressure of 755 torr. What gas pressure (in atm) is needed to change the volume to 776 cm3? Assume that the temperature and the amount of the gas do not change.

Answer 4

1.13 atm

Question 5

Suppose you have 2.9 L of helium at 1.0 atm of pressure. According to Boyle’s Law, at what pressure will cause the gas to expand to 3.5 L?

Answer 5

0.83 atm

Question 6

Suppose that you have a bicycle pump that is filled with air at a pressure of 1.00 atm. If the outlet valve is closed and the initial volume of the air inside is 975 cm3, what is the final pressure in the pump if the final volume is 438 cm3?

Answer 6

2.23 atm

Question 7

Suppose you fill a balloon with 23 L of gas at an atmospheric pressure of 1.0 atm. What will the new volume of the balloon be if you place it in an area that has an atmospheric pressure of 0.45 atm?

Answer 7

51 L

Question 8

Suppose the volume of the gas at the top of a closed can of mineral water is 1.9 cm3. When the can is opened (at standard conditions), the gas expands to a volume of 6.5 cm3. Use Boyle’s Law to find the original gas pressure inside the can before the can was opened. You can assume that the temperature and amount of gas are constant.

Answer 8

3.4 atm

Question 9

What will happen to the volume of a gas if the pressure is decreased? Assume that the amount of gas and the temperature remain constant.

Answer 9

The volume will increase.

Question 10

Suppose you are holding a balloon that contains 28 L of air at a standard atmospheric pressure of 14.7 lb / in2. If you squeezed the balloon until the pressure inside was 55 lb / in2, what would the final volume of the squeezed balloon be? Assume that the temperature remains constant.

Answer 10

7.5 L

Question 11

Suppose you have a cylinder and a movable piston containing helium gas. The volume of the cylinder is 2.4 L and the pressure of the gas is 4.8 atm. By what amount do you have to change the volume to lower the pressure to 1.0 atm?

Answer 11

9.1 L

Question 12

What is the final volume of a gas if 375 cm3 of the gas at 2.70 atm are compressed to a final pressure of 5.40 atm?

Answer 12

188 cm3