Question

Arrange the following four compounds in increasing order of their stability, if their heat of formation in standard states are given as: A. $-500~kJ~mol^{-1}$, B. $+700~kJ~mol^{-1}$, C. $-900~kJ~mol^{-1}$, D. $+250~kJ~mol^{-1}$.}

• A. C, A, D, B
• B. A, B, C, D
• C. B, D, A, C
• D. C, A, B, D

Hint:

More negative $\Delta H_{f}$ = More Chill = More Stable!

Answer 1

The Correct Option is C

Step 1: Concept Stability of a compound is inversely proportional to its enthalpy of formation ($\Delta H_{f}^{\circ}$).

Step 2: Meaning Exothermic compounds (negative $\Delta H_{f}^{\circ}$) are more stable than endothermic ones (positive $\Delta H_{f}^{\circ}$).

Step 3: Analysis The more energy released during formation (more negative value), the more stable the product. The values are: B (+700), D (+250), A (-500), C (-900).

Step 4: Conclusion The increasing order of stability is B < D < A < C. {red}{Final Answer: (C)