Question

Standard enthalpy and standard entropy changes for the oxidation of ammonia at `298 K` are `-382.64 kJ mol^(-1)` and `-145.6 jK^(-1)mol^(-1)` respectively. Standard Gibbs energy change for the same reaction at `298 K` is
A. `-523.2 kJ mol^(-1)`
B. `-22.1 kJ mol^(-1)`
C. `-339.3 kJ mol^(-1)`
D. `-439.3 kJ mol^(-1)`

Answer 1

Correct Answer - C
`NH_(3)(g)+(3)/(4)O_(2)(g)to(1)/(2)N_(2)(g)+(3)/(2)H_(2)O(l)`
`T=298 K`
`DeltaH=-382.64 kJ mol^(-1)`
`DeltaS=-145.6 JK^(-1) mol^(-1)`
`=-0.1456 kJ K^(-1) mol^(-1)`
`DeltaG=DeltaH-TDeltaS`
`=-382.64 kJ mol^(-1)-(298 K)xx(0.1456 k JK^(-1)mol^(-1))`
`=-382.64 kJ mol^(-1)+43.3888 kJ mol^(-1)`
`=-339.25 kJ mol^(-1)`