Question

Calculate the difference between heat of combustion of carbon monoxide gas at constant pressure and at constant volume at 27°C? (R = 2 cal K^-1 mol^-1).

Options

• 54 cal

• - 600 cal

• - 300 cal

• 27 cal

Answer 1

- 300 cal

Explanation:

Given,

T = 27°C = 300 K

R = 2 cal K^-1 mol^-1

Reaction for combustion of carbon monoxide is given as:

\[\ce{CO(g) + 1/2 O2(g) -> CO2(g)}\]

∴ Δn_g = 1 - 1.5 = - `1/2`

Now, the difference between heat of combustion of carbon monoxide gas at constant pressure and at constant volume is given by

ΔH - ΔU = Δn_g RT

∴ ΔH - ΔU = `- 1/2 xx 2 xx 300` = - 300 cal