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(b) the earth without its atmosphere would be inhospitably cold.

18 Given below are observations on molar specific heats at room temperature of some common
gases.

The measured molar specific heats of these gases are markedly different from those for mono
atomic gases. Typically, molar specific heat of a mono atomic gas is 2.92 cal/mol K. Explain this
difference. What can you infer from the somewhat larger (than the rest) value for chlorine ?

19 A child running a temperature of 101°F is given an antipyrin (i.e., a medicine that lowers fever)
which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought
down to 98° F in 20 minutes, what is the average rate of extra evaporation caused by the drug ?
Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the
child is 30 kg. The specific heat of human body is approximately the same as that of water, and
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latent heat of evaporation of water at that temperature is about 580 cal g .
20 State Newton’s law of cooling. Express it mathematically.