Question

For the spontaneous process $2F\left(g\right)\to F_2\left(g\right)$, the sign of $\Delta H$ and $\Delta S$ respectively, are:

• A. $+ve,-ve$
• B. $+ve,+ve$
• C. $-ve,-ve$
• D. $-ve,+ve$

Answer 1

Answer: (C)

$-ve,-ve$

The following spontaneous process is given:

$2F\left(g\right)\to F_2\left(g\right)$

We see that as the reaction occurs, the number of moles decreases due to which $\Delta S$ also decreases. Hence, $\Delta S$ is $-ve$.

However, since the process is spontaneous, $\Delta H$ also has to be negative so that $\Delta G$ is also negative $(\Delta G=\Delta H-T\Delta S)$.