In which of the given reactions, standard reaction entropy change `(DeltaS^(0))` is positive and standard Gibbs energy change `(DeltaG^(0))` decreases sharply with increasing temperature-

Options

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

Answer

A

Explanation

In the reaction, C(graphite)`+(1)/(2)O_(2)(g)toCO(g)`, number of gas molecules increases. As a result, entropy of the system increases `(DeltaS^(0)gt0)`.
We know, `DeltaG=DeltaH-TDeltaS` . . . [1]
For the given reaction `DeltaH^(0) lt0`, as it is a combustion reaction. since `DeltaH^(0) lt0 and DeltaS^(0) gt0`, according to the reaction [1], `DeltaG^(0)` decreases with rise in temperature.