At a certain temperature and pressure, `DeltaH=0` for the reaction: X+X=`X_(2)`. Show that the reaction is non-spontaneous at this temperature and pressure.

Explanation

At a certain temperature and pressure, for a chemical reaction, `DeltaG=DeltaH-TDeltaS`.
Now, `DeltaH=0` for given the reaction. So, `DeltaG=-TDeltaS`
In the given reaction, `X_(2)` is produced from two atoms of X. So, the entropy of the system decreases. So, `DeltaSlt0`
`DeltaG=Txx`(negative quantity)=positive quantity
The positive value of `DeltaG` indicates that the reaction is non-spontaneous.