Calculate the work done during combustion of 0.138 kg of ethanol, `C_2 H_5 OH_((l))` at 300 K.
Given : R 8.314 `"JK"^(-1)"mol"^(-1)`, molar mass of ethanol `=" 46 g mol"^(-1)`

Options

A. `-7482 J`
B. `7482 J`
C. `-2494 J`
D. 2494 J

Answer

A

Explanation

`C_2 H_5 OH_((l))+3O_(2(g))to 2CO_(2(g))+3H_2O_((l))`
`Delta n = 2- 3 =-1`
`w=-Deltan" RT"`
`:." "w = + (1) xx 3x314 xx 300`
`:." "W = 2494.2 J`
For 46 gm ethanol work done = 2494.2 J
`:." "138` gm ethanol work done `= x J`
`x = (138 xx 2494.2)/(46) = 7482.6 J`