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Delta(f)U^(@) of formation of CH(4)(g) a...

`Delta_(f)U^(@)` of formation of `CH_(4)(g)` at certain temperature is `- 393 kJ mol^(-1)`. The value of `Delta_(f)H^(@)`

A

zero

B

`lt Delta_(f)U^(@)`

C

`gt Delta_(f)U^(@)`

D

equal to `Delta_(f)U^(@)`

Text Solution

Verified by Experts

The correct Answer is:
B
`Delta_(f) H^(@) = Delta_(f) U^(@) + Delta n_(g) RT`
For the reaction,
`C(s) + 2H_(2)(g) rarr CH_(4)(g)`
:. `Delta n_(g) = 1 - 2 = - 1`
:. `Delta_(f) H^(@) = Delta_(f) U^(@) - 1 RT`
or `Delta_(f) U^(@) = Delta_(f) H^(@) + RT`
or `Delta_(f) H^(@) lt Delta_(f) U^(@)`
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