Pressure of a gas is defined as the force exerted by gas molecules per unit area on the walls of the container due to their continuous random motion.
Gas molecules are in continuous random motion. When they collide with the walls of the container, they exert force on the walls.
The total force exerted per unit area gives rise to gas pressure.
Pressure = Force / Area
According to kinetic theory of gases, pressure is directly related to the motion of gas molecules.
Greater the speed of molecules, greater is the pressure.
On increasing temperature, the speed of gas molecules increases, resulting in an increase in gas pressure (for constant volume).
The SI unit of pressure is pascal (Pa).
Q1. Pressure of a gas is due to: A) Weight of gas B) Intermolecular attraction C) Collision of molecules with container walls D) Volume of gas molecules Answer: C Q2. Gas pressure is defined as: A) Force × area B) Area / force C) Force / area D) Force + area Answer: C Q3. SI unit of pressure is: A) Joule B) Newton C) Pascal D) Watt Answer: C Q4. On increasing temperature of a gas at constant volume, pressure: A) Decreases B) Remains constant C) Increases D) Becomes zero Answer: C Q5. Pressure of a gas depends on: A) Speed of molecules only B) Number of molecules only C) Temperature only D) Speed, number and temperature of molecules Answer: D Q6. Faster moving gas molecules exert: A) Less pressure B) More pressure C) No pressure D) Constant pressure Answer: B Q7. Pressure of a gas is independent of: A) Temperature B) Speed of molecules C) Collisions with walls D) Colour of gas Answer: D Q8. Which phenomenon explains gas pressure? A) Diffusion B) Brownian motion C) Collision of molecules D) Refraction Answer: C
Force exerted per unit area by gas molecules on container walls.
Continuous random motion and collision of molecules.
Pressure = Force / Area
Pascal (Pa)
MCQs are frequently asked on origin of gas pressure, definition and factors affecting pressure.
