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Which one of the following substances has constant specific heat at all pressures and temperatures?

Which one of the following substances has constant specific heat at all pressures and temperatures? Correct Answer Mono-atomic gas

Specific heat: It is defined as the energy required to raise the temperature of a unit mass of substance by one degree. In general this energy depend on how the process is executed.

In thermodynamics we deal with two kinds of specific heats

Specific heat at constant volume: It is the amount of energy required to raise the temperature of the substance by one degree if the volume is maintained constant.

Specific heat at constant pressure: It is the amount of heat required to raise the temperature of the substance by one degree if the temperature of the substance is raised by one degree if the pressure is held constant.

Specific heat for ideal gases

Monoatomic gas: The specific heat of monoatomic gases remain constant over the entire temperature range. 

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Diatomic or triatomic gases: The specific heats of diatomic and triatomic gases increase with the increase in temperature. This variation is approximated as linear variation over small temperature intervals. Therefore the specific heats can be assumed as constant average specific heat values. 

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