# The specific heat at constant pressure is greater than that of the same gas at constant volume because A. at constant volume work is done in expanding the gas B. at constant pressure work is done in expanding the gas C. the molecular attraction increases more at constant pressure D. the molecular vibration increases more at constant pressure

Saurabh Koranglekar
4 years ago
CP​>CV​
CP​is greater thanCV​because when a gas is heated at constant volume, no external work is done and so the heat supplied is consumed only in increasing the internal energy of a gas.
But if the gas is heated at constant pressure, the gas expands against the external pressure so does some external work. in this case the heat is used up in increasing the internal energy of the gas and in doing some external work.
Since the internal energy depends only on temperature, for the same rise of temperature the internal energy of a mass of a gas will increase by the same amount whether the pressure or volume remains constant. But since external work is additionally done for constant pressure than at constant volume to produce the same rise in temperature of the gas.
Above is the reason whyCP​is greater thanCV​.
Vikas TU
14149 Points
4 years ago
The heat capacity at constant pressure CP is greater than the heat capacity at constant volume CV , because when heat is added at constant pressure, the substance expands and work. QV = CV △T = △U + W = △U because no work is done