Question

When an ideal diatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is:

• A. 2/5
• B. 3/5
• C. 3/7
• D. 5/7

Answer 1

Answer: (D)

5/7

Answer 2

dQ = n C_PdT

= n (C_v + R) dT

dQ = n C_vdT + n RdT

n C_PdT = n C_vdT + n RdT

n C_vdT increases internal energy.

∴ Fraction of energy that increases internal energy is

$\frac{C_{v}}{C_{P}}$ = $\frac{5}{7}$

Hence, D is correct Answer.