Question

The following statements are given: (i) The third law of thermodynamics deals with the entropy of a substance at the absolute zero temperature.
(ii) Entropy of any non-crystalline structure is zero at absolute zero temperature.
(iii) At the absolute zero temperature, the crystal structure has maximum degree of order.
(iv) The thermal energy of the substance at absolute zero temperature is maximum.
The correct option describing these statements is:

• A. Only (i) is correct
• B. Only (ii) is correct
• C. Both (i) and (iii) are correct
• D. Both (i) and (iv) are correct

Hint:

Remember: At $T=0$ K, entropy $\to 0$ for a perfect crystal. Amorphous solids retain residual entropy, and thermal energy is minimum at absolute zero.

Answer 1

The Correct Option is C

Step 1: Recall the third law of thermodynamics.
The third law states: "The entropy of a perfect crystalline substance approaches zero as the temperature approaches absolute zero." Thus, statement (i) is correct.
Step 2: Check statement (ii).
Entropy of non-crystalline (amorphous) substances does not become zero at absolute zero because of residual entropy. So, statement (ii) is incorrect.
Step 3: Check statement (iii).
At absolute zero, a perfect crystal has maximum order (entropy = 0). Thus, statement (iii) is correct.
Step 4: Check statement (iv).
At absolute zero, thermal energy is minimum (not maximum). So, statement (iv) is incorrect. Final Answer: \[ \boxed{\text{Both (i) and (iii) are correct (Option C)}} \]