Calculate difference in specific heats for `1` gram of air at `N.T.P`. Given density of air at N.T.P. is `1.293 g litre^(-1), j=4.2xx10^(7)" erg "cal^(-1)`.

Explanation

PV=mrT
The difference in specific heats, `r=(P)/(rhoT)`
`P=1.013xx10^(5)N//m^(2), T=273K,`
`=1.25xx(10^(-3)kg)/(10^(3)cm^(3))=(1.25xx10^(-3)kg)/(10^(3)xx10^(-6)m^(3))=1.25 kg//m^(3)`
`therefore r=(1.013xx10^(5))/(1.25xx273)=296.8J//Kg K`
`therefore` The difference of specific heats
=0.0768 K Cal/kg-K.