It the specific heat of a gas at constant pressure, C_p is . The atomicity of the gas would be

CONCEPT:

• The molar specific heat capacity of a gas at constant volume is defined as the amount of heat required to raise the temperature of 1 mol of the gas by 1 °C at the constant volume.

• The molar specific heat of a gas at constant pressure is defined as the amount of heat required to raise the temperature of 1 mol of the gas by 1 °C at the constant pressure.

• The ratio of the two principal specific heat is represented by γ.

• The value of γ depends on the atomicity of the gas.

EXPLANATION:

• For monoatomic gas, 

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• For diatomic gas,

• Therefore, option 1 is correct.

Additional Information   

• Specific heat capacity at constant volume (CV): It is the amount of heat required to raise the temperature of 1 kg of gas maintained at constant volume by 1 degree Celcius.
• Specific heat capacity at constant volume (C_V) for monoatomic gas is, 

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• Specific heat capacity at constant volume (CV) for for diatomic gas,