Question

The $\Delta G^{\circ}$ is negative for the reduction of $Cr _{2} O _{3}$ with Al but the reaction does not take place at room temperature because

• A. the net value of $\Delta G^{\circ}$ becomes positive
• B. the orientation of molecules of $Al$ and $Cr _{2} O _{3}$ is not process
• C. certain amount of activation energy is required to start the reaction
• D. melting point of $Cr _{2} O _{2}$ is very high so no reaction take place

Answer 1

Answer: (C)

Several spontaneous reactions also require a certain amount of activation energy to overcome the forces of attraction, therefore heating is required.