Question

When a gas is expanded at constant temperature

(A) the pressure decreases

(B) the kinetic energy of the molecules remain the same

(C) the kinetic energy of the molecules decreases

(D) the number of molecules of the gas increases

Answer 1

Correct option (A) the pressure decreases

(B) the kinetic energy of the molecules remain the same

Explanation : 

PV = nRT

(A) If gas is allowed to expand at constant temperature, P decreases (due to increase in V), hence true.

(B) K.E. = (3/2)nRT

KE ∝ temperature T hence (B) is also true.

(A) and (B) correct.