Question

For the reaction
$ A ( g )+ B ( g ) \rightarrow 3 C ( g ), 298 K $
If $\Delta U^{\circ}=-10 kJ$ and $\Delta S^{\circ}=40 JK ^{-1}$ then $\Delta G ^{\circ}$ for the reaction is nearly

• A. $6.1 kJ$
• B. $12.2 kJ$
• C. $-19.4 kJ$
• D. $-48.8 kJ$

Answer 1

Answer: (C)

$ \Delta H ^{\circ} =\Delta U ^{\circ}+\Delta n _9 RT $
$ =-10+(3-1-1) \times 8.314 \times 10^{-3} \times 298$
$ =-7.5 kJ $
$ \Delta G ^{\circ} =\Delta H ^{\circ}- T \Delta S ^{\circ} $
$ =-7.5-298 \times 40 \times 10^{-3} $
$ =-19.4 kJ $