At `0^(@)C` the entropy of a perfectly crystalline solid is zero.

Answer

To determine whether the statement "At 0°C the entropy of a perfectly crystalline solid is zero" is true or false, we can follow these steps:

### Step 1: Understand the Third Law of Thermodynamics
The Third Law of Thermodynamics states that the entropy of a perfectly crystalline substance approaches zero as the temperature approaches absolute zero (0 Kelvin).

### Step 2: Convert Temperature to Kelvin
0°C is equivalent to 273.15 K. Therefore, we need to evaluate the statement at this temperature.

### Step 3: Analyze the Entropy at 0 K
According to the Third Law, the entropy of a perfectly crystalline solid is exactly zero at 0 K (absolute zero). This means that at any temperature above 0 K, including 273.15 K (0°C), the entropy will be greater than zero.

### Step 4: Conclusion
Since the entropy of a perfectly crystalline solid is zero only at 0 K (or -273.15°C), the statement that "At 0°C the entropy of a perfectly crystalline solid is zero" is false.

### Final Answer
The statement is **false**.

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