Question

Which of the following statement is correct?

• A. $\Delta S$ for $\frac{1}{2}Cl_2(g) \rightarrow Cl(g)$ is positive.
• B. $\Delta E < 0$ for combustion of $CH_4(g)$ in a sealed container with rigid adiabatic system.
• C. $\Delta G$ is always zero for a reversible process in a closed system.
• D. $\Delta G^\circ$ for an ideal gas reaction is a function of pressure.

Answer 1

Answer: (A)

$\Delta S$ for $\frac{1}{2}Cl_2(g) \rightarrow Cl(g)$ is positive.

Answer 2

The entropy change ($\Delta S$) is positive for the reaction $\frac{1}{2}Cl_2(g) \rightarrow Cl(g)$ because one mole of gas is converted into two moles, increasing the disorder. Therefore, entropy increases.

In a rigid adiabatic system, $\Delta E = 0$ because no heat or work is exchanged with the surroundings.

$\Delta G = 0$ for a reversible process at constant temperature and pressure, but not always.

$\Delta G^\circ$ is the standard Gibbs free energy change, which is a function of temperature, not pressure.