Is the molar specific heat of a solid a constant value? Explain.

(A) According to the Dulong-Petit law,the molar specific heat capacity of a solid at room temperature is approximately constant and is given by $C_v = 3R$,where $R$ is the universal gas constant. Since $R \approx 2 \text{ cal/mol K}$,the value is approximately $3 \times 2 = 6 \text{ cal/mol K}$. However,the specific value $3 \text{ cal/mol K}$ mentioned in the prompt is incorrect; the correct classical value is $3R \approx 6 \text{ cal/mol K}$.