Question

Consider the following volume−temperature (V−T) diagram for the expansion of 5 moles of an ideal monoatomic gas.

Considering only P-V work is involved, the total change in enthalpy (in Joule) for the transformation of state in the sequence X → Y → Z is ______. 

[Use the given data: Molar heat capacity of the gas for the given temperature range, \(C_{V,m} = 12 \,J \,K^{-1} mol^{-1}\) and gas constant, \(R = 8.3 \,J \,K^{-1} mol^{-1}\)]

Answer 1

Correct answer is : 8120

\(X \rightarrow Y\) is an isothermal process an ideal gas:

\(\Delta\)H = 0

\(Y \rightarrow Z\) is an isochoric process

\(\therefore w = 0\)

\(\Delta U = nC_{V,m} (T_2 - T_1)\)

= 5 x 12 (415 - 335) 

= 4800 J

\(\Delta H = \Delta U + \Delta(PV)\)

\(= \Delta U + nR\Delta T\)

= 4800 + 5 x 8.3 x (415 - 335) 

= 8120 J