Question

When an ideal gas is compressed isothermally then its pressure increases because

• A. its potential energy decreases
• B. its kinetic energy increases and molecules move apart
• C. its number of collisions per unit area with walls of container increases
• D. molecular energy increases

Answer 1

The correct option is C its number of collisions per unit area with walls of container increases

It is meaningless to talk about individual speeds of molecules of a gas, thus we only talk about average speed.

For the molecule of a gas in thermal equilibrium i.e, constant temperature average speed would be constant as $Vav=\sqrt{\frac{8KT}{\pi M}}$

$Vav\propto \sqrt{T}$

Hence, the answer is its number of collisions per unit area with walls of container increases.