Question

`DeltaU^(Θ)` of combustion of methane is `-XkJ mol^(-1)`. The value of `DeltaH^(Θ)` is
A. `=DeltaU^(Θ)`
B. `gt DeltaU^(Θ)`
C. `lt DeltaU^(Θ)`
D. zero

Answer 1

Correct Answer - c
The balance equation for combustion of methane with be
`CH_(4)(g)+2O_(2)(g) rarr CO_(2)(g)+2H_(2)O(l)`
Thus, `Deltan_(g)=(n_(p)-n_(r))_(g)=1-3=-2`
`DeltaH^(Θ)=DeltaU^(Θ)+Deltan_(g)RT=-X-2 RT`
Thus, `DeltaH^(Θ) lt DeltaU^(Θ)`