Gas Pressure

Question 1

Gas pressure in a container is caused by:

Accepted Answer

Gas molecules colliding with the container walls — Gas pressure arises from molecular collisions with the walls.

Question 2

Which instrument uses a liquid-filled U-tube to measure gas pressure?

Accepted Answer

Manometer — A manometer is a U-tube used to measure gas pressure.

Question 3

A gas exerts 300 N on a piston of area 0.015 m². The gas pressure is:

Accepted Answer

20 000 Pa — P = F / A = 300 / 0.015 = 20 000 Pa.

Question 4

In a water manometer, the open side is 0.10 m higher than the gas side (ρ = 1000 kg m⁻³, g = 10 m s⁻²). The gas pressure exceeds atmospheric by:

Accepted Answer

1000 Pa — Excess pressure = ρgh = 1000 × 10 × 0.10 = 1000 Pa.

Question 5

At fixed volume, increasing the temperature of a gas causes its pressure to:

Accepted Answer

Increase — Higher temperature means faster molecules and more forceful collisions, raising pressure.

Question 6

If the level of liquid in a manometer is equal on both sides, the gas pressure equals:

Accepted Answer

Atmospheric pressure — Equal levels mean no pressure difference, so gas pressure equals atmospheric.

Question 7

A manometer uses mercury (ρ = 13 600 kg m⁻³). A height difference of 0.05 m corresponds to a pressure difference of (g = 10 m s⁻²):

Accepted Answer

6800 Pa — ΔP = ρgh = 13 600 × 10 × 0.05 = 6800 Pa.

Question 8

If a gas is compressed into a smaller volume at constant temperature, its pressure:

Accepted Answer

Increases — Smaller volume means more frequent collisions per unit area, so pressure increases (Boyle's law).

Question 9

The gas pressure measured relative to atmospheric pressure is found using the level difference and the formula:

Accepted Answer

P = ρgh — The pressure difference from the liquid column is ρgh.

Question 10

A gas exerts 800 N on an area of 0.04 m². Its pressure is:

Accepted Answer

20 000 Pa — P = F / A = 800 / 0.04 = 20 000 Pa.