A certain gas in expanded from `(1L, 10 atm)` to `(4L, 5 atm)` against a constant external pressure of `1atm`. If the initial temperature of gas is `300K` and heat capacity for the process is `50J^(@)C^(-1)`, the enthalpy change during the process is: (use: `1L-atm = 100J)`

Options

A. `Delta H= 15 KJ`
B. `Delta H= 15.7 KJ`
C. `Delta H=14.4 KJ`
D. `Delta H=14.7 KJ`

Answer

B

Explanation

`{:("State" 1,,rarr,,"State" 2),((1 L","10atm","300K),,,,(4 L","5atm","600K)):}`
Heat gi ven `q=50'(600-300)= 15000 J`
`W= -P_(ext)(V_(2)-V_(1))= -1(4-1)= -3L atm = -300 J`
`Delta E= q+W=15000-300=14700 J`
`Dleta H= Delta E+P_(2)V_(2)-P_(1)V_(1)=14700 J+(20-10)xx100 J=15.7KJ`