Question:medium

According to the Dulong and Petit's law, the atomic heat of an element at constant volume:

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Dulong-Petit is a classical high-temperature limit. It fails at low temperatures where quantum effects become important. Einstein's and Debye's models were developed to explain this low-temperature deviation.
Updated On: Feb 10, 2026
  • increases with increase of temperature
  • decreases with increase of temperature
  • becomes zero at absolute zerop
  • is constant
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The Correct Option is D

Solution and Explanation

The Dulong and Petit law, a classical thermodynamic principle derived from the equipartition theorem, quantifies the molar specific heat capacity of solid elements. At elevated temperatures, this law posits that the molar specific heat at constant volume (\(C_V\)) for all solid elements remains approximately constant, equaling \(3R\), where \(R\) is the universal gas constant.\[ C_V \approx 3R \approx 3 \times 8.314 \, \text{J/(mol}\cdot\text{K)} \approx 25 \, \text{J/(mol}\cdot\text{K)} \]Molar specific heat is also referred to as "atomic heat." The law's prediction is that this value is constant, irrespective of the material or temperature at high temperatures. While contemporary quantum mechanics, such as the Debye model, indicates a decrease in specific heat towards zero at absolute zero, the Dulong and Petit law itself asserts a constant value. The query specifically seeks the law's statement, not experimental observations at low temperatures.
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