JEE Main · 2019 · 08 Apr 2019 · Shift 1 · Chemical Thermodynamics

For silver

C_{P} (J K^{- 1} mol^{- 1}) = 23 + 0.01 T

. If the temperature (T) of 3 moles of silver is raised from 300 K to 1000 K at 1 atm pressure, the value of

Δ H

will be close to:

Answer: (B)

Solution

The enthalpy change on heating is

Δ H = n \int_{T_{1}}^{T_{2}} C_{p} d T

, so integrate the temperature-dependent heat capacity for

3

mol:

Δ H = 3 \int_{300}^{1000} (23 + 0.01 T) d T = 3 [23 T + 0.005 T^{2}]_{300}^{1000}

. The bracket gives

23 (700) + 0.005 (1 0^{6} - 9 \times 1 0^{4}) = 16100 + 4550 = 20650

J, and multiplying by

3

yields

Δ H \approx 61950

J, close to

62

kJ.

JEE Main · 2019 · 08 Apr 2019 · Shift 1 · Single correct option