A gas `(C_(v.m) = (5)/(2)R)` behaving ideally is allowed to expand reversibly and adiabatically from `1` litre to `32` litre. Its initial temperature is `327^(@)C`. The molar enthalpy change (in `J//mol`) for the process is :

Options

A. `-1125 R`
B. `-675`
C. `-1575 R`
D. 101 R

Answer

C

Explanation

`(T_(2))/(T_(1)) = ((V_(1))/(V_(2)))^(gamma-1), T_(2) = T_(1)((1)/(32))^((7)/(5)-1) = 600((1)/(2^(5)))^(2//5)`
`= 600(0.5)^(2)=150K, Delta H_(m) = (7)/(2)R xx(150-600) = -1575 R`