Question

Calculate the work done during combustion of 0.138 kg of ethanol, `C_(2)H_(5)OH_(1)` at 300 K.
Given: `R= 8.314 JK^(-1) mol^(-1)` molar mass of ethanol = `46 gm mol^(-1)`
A. `-7482` J
B. 7482 J
C. `-2494` J
D. 2494 J

Answer 1

Correct Answer - B
`underset(0.138 kg) underset(darr)(C_(2)H_(5)OH) +underset(3)underset(darr)(3O_(2)) to underset(2)underset(darr)(2CO_(2)) +underset(3)underset(darr)(3H_(2)O)`
Hence Mole `=138/46 =3 `moles of `C_(2)H_(5)OH`.
`3C_(2)H_(5)OH(l) + 9O_(g) to 6CO_(2)(g) + 9H_(2)O (u)`
`deltan = 6-9 =-3`
Work =`-deltanRT`
`=-(-3) xx 8.314 xx 300`
`=-7482` J