Question

For a particular reaction, $\Delta H^o=-38.3kJ$ and $\Delta S^o=-113J{K}^{-1}{mol}^{-1}$. This reaction is:

• A. spontaneous at all temperatures
• B. non-spontaneous at all temperatures
• C. spontaneous at temperatures below ${66}^{o}C$
• D. spontaneous at temperatures above ${66}^{o}C$

Answer 1

The correct option is C spontaneous at temperatures below ${66}^{o}C$

$\left(\Delta G\right)=$$\left(\Delta H\right)-T$$\left(\Delta S\right)$

for spontanious $\left(\Delta G\right)$ must be negative.

$\left(\Delta H\right)-T$$\left(\Delta S\right)$<0

$\left(\Delta H\right)<T$$\left(\Delta S\right)$

$\left(\Delta H\right)$/$\left(\Delta S\right)$<$T$

$(-38300)$/$(-113)$<$T$

$339K$<$T$

${66}^{o}C$<$T$