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delta(f) U^(Ө) "of formation of" CH(4)(g...

`delta_(f) U^(Ө) "of formation of" CH_(4)(g)` at a certain temperature is `-393Jmol^(-1).` The value of `delta H^(Ө)is:`

A

Zero

B

`lt Delta_(f) U^(Ɵ)`

C

`gt Delta_(f)U^(Ɵ)`

D

Equal to `Delta_(f)U^(Ɵ)`

Text Solution

Verified by Experts

The correct Answer is:
B
The reaction is `C(s) + 2H_(2)(g) rarr CH_(4)(g)`
`Delta n_(g)= 1-2= -1`
`Delta_(f)H^(Θ) = Delta_(f)U^(Θ) + Delta n_(g)RT`
As `Delta n_(g)= -1`
`therefore Delta_(f) H^(Θ) lt Delta_(f) U^(Θ)`
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