Given below are observations on molar specific heats at room temperature of some common gases. Gas Molar specific heat (Cv ) (cal mo1¯¹ K¯¹) Hydrogen 4.87 Nitrogen 4.97 Oxygen 5.02 Nitric oxide 4.99 Carbon monoxide 5.01 Chlorine 6.17 The measured molar specific heats of these gases are markedly different from those for monatomic gases. Typically, molar specific heat of a monatomic gas is 2.92 cal/mol K. Explain this difference. What can you infer from the somewhat larger (than the rest) value for chlorine ?
A monatomoc gas has only three translational degrees of freedom. A diatomic gas molecule, apart from translational behavior, also shows rotational as well as vibrational behavior. So, to raise the temperature of 1 mole of a diatomic gas through 1 o C , the heat supplied to the molecules will be needed not only for translational energy but to increase the rotational and vibrational energies also.
Thus, the molar specific heat for diatomic gases is more than that of monatomic gases.
The higher value of molar specific heat of chlorine, as compared to hydrogen, nitrogen, oxygen etc., is due to fact that at room temperature chlorine usually have rotational motion apart from translational and vibrational motion, while elements other than chlorine has translational and vibrational motion only.
That is why the chlorine has larger value of the molar specific heat.
A monatomoc gas has only three translational degrees of freedom. A diatomic gas molecule, apart from translational behavior, also shows rotational as well as vibrational behavior. So, to raise the temperature of
Thus, the molar specific heat for diatomic gases is more than that of monatomic gases.
The higher value of molar specific heat of chlorine, as compared to hydrogen, nitrogen, oxygen etc., is due to fact that at room temperature chlorine usually have rotational motion apart from translational and vibrational motion, while elements other than chlorine has translational and vibrational motion only.
That is why the chlorine has larger value of the molar specific heat.
