Specific Heat capacities of a gas
When a gas is heated, its volume and pressure change to a greater extent. The gas can be heated at constant pressure as well as at constant volume the amount of heat required to raise the temperature of a gas through same value at constant pressure and at constant volume is different. So, a gas has two types of specific heat capacities: (1) At constant pressure Cp and (2) At constant volume Cv.
1. Heat capacity at constant volume: It is defined as the amount of heat required to increase the temperature of 1kg substance by 1 K at constant volume.
Molar heat of a gas at constant pressure: It is defined as the amount of heat required to raise the temperature of one-mole gas through one Kelvin at constant pressure. It is denoted by Cv and its unit is J mol-1 K-1. If Q is the amount of heat required to raise the temperature of n-mole of a gas through ΔT at constant pressure, the molar heat capacity of the gas is
2. Heat capacity at constant pressure: It is defined as the amount of heat required to increase the temperature of 1kg substance by 1 K at constant pressure.
Molar heat of a gas at constant pressure: It is defined as the amount of heat required to raise the temperature of one-mole gas through one Kelvin at constant pressure. It is denoted by Cp and its unit is J mol-1 K-1.
If Q is the amount of heat required to raise the temperature of n-mole of a gas through ΔT at constant pressure, the molar heat capacity of the gas is
Cp = Q/ n ΔT
If M is the molecular mass then
Cp = Mcp
Important question:
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