Question

Which among the following will definitely cause the volume of a gas to increase?
I. Decreasing the pressure with the temperature held constant
II. Increasing the pressure with a temperature decrease
III. Increasing the temperature with a pressure increase

• A. I only
• B. II only
• C. I and III only
• D. II and III only
• E. I, II and III

Answer 1

Answer: (A)

I only

I. Decreasing the pressure with the temperature held constant will definitely cause the volume of a gas to increase.
When temperature is held constant, the volume of gas is inversely proportional to pressure.
$V\propto \frac{1}{P}$
When pressure is decreased, volume is increased.
II. Increasing the pressure with a temperature decrease will cause the volume of a gas to decrease.
$V\propto \frac{T}{P}$
III. Increasing the temperature with a pressure increase may increase or decrease the volume.