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

Total heat energy supplied to raise temperature of a diatomic gas at constant pressure  ${\text{=nC}}_{\text{p}}\text{ΔT}$

 Total rise in internal energy ${\text{=nC}}_{\text{v}}\text{ΔT}$

Thus fraction of heat energy utilized in increasing internal

Energy $\text{=}\frac{{\text{c}}_{\text{v}}}{{\text{c}}_{\text{p}}}\text{=}\frac{\frac{\text{f}}{\text{2}}}{\frac{\text{f}}{\text{2}}\text{+1}}$

$\text{=}\frac{\text{f}}{\text{f+2}}$

Where f is the number of degree of freedom of the gas.

For diatomic gas, f = 5

Thus fraction $\text{=}\frac{5}{7}$