Question

The value of enthalpy change `(DeltaH)` for the reaction
`C_(2)H_(5)OH (l)+3O_(2) (g) rarr 2CO_(2) (g) +3H_(2)O (l)`
at `27^(@)C` is `-1366.5 kJ mol^(-1)`.
The value of internal energy change for the above reactio at this temperature will be
A. `-1371.5 kJ`
B. `-1369.0 kJ`
C. `-1364.0 kJ`
D. `-1361.5kJ`

Answer 1

Correct Answer - C
`C_(2)H_(5)OH(l)+3O_(2)(g)to2CO_(2)(g)+3H_(2)O(s)`
`Deltan(g)=2-3=1`
`DeltaU=DeltaH-Deltan(g)RT=-1366.5 kJ mol^(-1)`
`-(-1xx8.314xx10^(-3)xx300kJ mol^(-1))`
`=-1366.5+2.4942=-1364 kJ mol^(-1)`