For a chemical reaction the values of `DeltaH` and `DeltaS` at 300 K are - 10 kJ `"mol"^(-1)` and -20 J `"deg"^(-1) "mol"^(-1)` respectively. What is the value of `DeltaG` of the reaction? Calculate the `DeltaG` of a reaction at 600K assuming `DeltaH` and `DeltaS` values are constant. Predict the nature of the reaction.

Explanation

`DeltaH=-10 "kJ mol"^(-1) =-10000 "J mol"^(-1)`
`DeltaS=-20 J K^(-1) "mol"^(-1)`
T=300 K
`DeltaG`=?
`DeltaG=DeltaH-TDeltaS`
`DeltaG=-10 "kJ mol"^(-1) -300 K xx (-20 xx10^(-3))kJ K^(-1) "mol"^(-1)`
`DeltaG=(-10+6) "kJ mol"^(-1)`
`DeltaG=-4 "kJ mol"^(-1)`
At 600 K
`DeltaG=-10 "kJ mol"^(-1) -600 K xx(-20 xx10^(-3))kJ K^(-1) "mol"^(-1)`
`DeltaG=(-10+12) "kJ mol"^(-1)`
`DeltaG=+2 kJ mol^(-1)`
The value of `DeltaG` is negative at 300K and the reaction is spontaneous, but at 600K the value `DeltaG` becomes positive and the reaction is non-spontaneous.