Question

One mole of an ideal monoatomic gas is at temperature of 300 K₀ . Its volume is doubled keeping its pressure constant. The change in internal energy is

(1) 3.735 x 10³ J

(2) 6.225 x 10³ J

(3) 8.715 x 10³ J

(4) 6.225 x 10² J

Answer 1

(1) 3.735 x 10³ J

At constant pressure, volume is directly proportional to temperature. Therefore

ΔU = The change in internal energy = nC_v (ΔT)

= f/2 nR (T₂ - T₁), where f = number of degrees of freedom and equals 3 for a monoatomic gas.