In which of the following reactions,standard reaction entropy change`(DeltaS^(@))`is positive and standard Gibb,s energy change`(DeltaG^(@))`decreases sharply with increasing temperature?

Options

A. `C("graphite")+1//2O_(2)(g)toCO_(2)(g)`
B. `CO(g)+(1)/(2)O_(2)(g)toCO_(2)(g)`
C. `Mg(s)+(1)/(2)O_(2)(g)toMgO(g)`
D. `(1)/(2)C("graphite")+(1)/(2)O_(2)to(1)/(2)CO_(2)(g)`

Answer

A

Explanation

For the reaction, `C("graphite")+(1)/(2)O_(@)toCO_(2)(g)`
`Deltang=1-(1)/(2)=-1//2`
Thus `DeltaS` is positive due to increase in the number of gaseous moles. According to Gibbs Helmholtz equation `DeltaG=DeltaH-TDeltaS`. As `DeltaS` is positive, increase in temperature will make `TDeltaS` more negative and `DeltaG` will decrease.