Question

Which of the following conditions regarding the chemical process ensures its spontaneity at all temperatures?

• A. \(\Delta H<0; \Delta S<0\)
• B. \(\Delta H>0; \Delta S<0\)
• C. \(\Delta H<0; \Delta S>0\)
• D. \(\Delta H>0; \Delta S>0\)

Hint:

Think of it as: exothermic (\(\Delta H<0\)) and increasing disorder (\(\Delta S>0\)) will always favor a spontaneous process.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Spontaneity of a process is determined by Gibbs free energy change: \(\Delta G = \Delta H - T\Delta S\). For spontaneity, \(\Delta G<0\).
Step 2: Detailed Explanation:
\begin{itemize} \item (A) \(\Delta H<0, \Delta S<0\): \(\Delta G\) is negative at low temperatures, positive at high temperatures. Spontaneous only at low temperatures. \item (B) \(\Delta H>0, \Delta S<0\): \(\Delta G\) is always positive. Non-spontaneous at all temperatures. \item (C) \(\Delta H<0, \Delta S>0\): \(\Delta G\) is always negative. Spontaneous at all temperatures. \item (D) \(\Delta H>0, \Delta S>0\): \(\Delta G\) is negative at high temperatures, positive at low temperatures. Spontaneous only at high temperatures. \end{itemize}
Step 3: Final Answer:
The condition for spontaneity at all temperatures is \(\Delta H<0\) and \(\Delta S>0\), option (C).