Question

For the reaction, $X_2{O}_4\left(i\right)\to 2X{O}_2\left(g\right)$, $\Delta U=2.1kcal,\Delta s=20cal{K}^{-1}$ at 300 K.

Hence, $\Delta G$ is:

• A. 2.7 k cal
• B. -2.7 k cal
• C. 9.3 k cal
• D. -9.3 kcal

Answer 1

The correct option is B -2.7 k cal

The relationship between the enthalpy change and the change in internal energy is as shown below.

$\Delta H=\Delta U+\Delta n_{g}RT$

Substitute values in th above expression.

$=2.1+\frac{2\times 2\times 300}{1000}=3.3$

The relationship between the change in free energy, the enthalpy change and the entropy change is as shown below.

$\Delta G=\Delta H-T\Delta s$

$=3.3-300\times \frac{26}{1000}=3.3-6=-2.7Kcal$

Hence, the change in the free energy is -2.7 K cal.