The pressure exerted by a gas is a function of the

Analyze the question: It asks what the pressure of a gas depends on, according to the kinetic theory of gases.

Concept: Gas pressure comes from gas molecules colliding with the walls of their container. Each collision exerts a small force on the wall, and the pressure is the total force of these collisions per unit area of the wall.

From kinetic theory, P = (1/3)(N/V)m⟨c²⟩, so pressure depends on:

• the number of molecules per unit volume,
• the mass of each molecule,
• the average speed of the molecules (through the mean square speed).

These factors all affect how often and how hard the molecules strike the walls. In effect, pressure is determined by the frequency and force of the collisions with the container walls.

Checking the options:

• A. Total volume of the gas: Volume affects pressure (Boyle's law), but a gas always fills its container. Volume is a condition, not the direct cause of the pressure. It acts by changing how often molecules collide with the walls.
• B. Speed of the molecules: Speed contributes, but it is only one factor. Speed alone doesn't give the pressure.
• C. Mass of each molecule: This is also only one factor.
• D. Frequency of collision: This directly describes the cause of pressure. More frequent collisions mean greater pressure. Changes in volume, temperature (speed) and number of molecules all affect pressure by changing the collision frequency.

Note: The wording "collision between gaseous molecules" is a bit loose, since the pressure really comes from collisions with the container walls.

Answer: D

Exam tip: When you see "pressure of a gas," think "molecules hitting the walls." Anything that increases the rate of collisions (higher temperature, smaller volume, more molecules) increases the pressure.