Calculate the value of mechanical equivalent of heat from the following data. Specific heat capacity of air at constant volume and at constant pressure are `4.93 cal//mol-K` and `6.90 cal//mol-K` respectively. Gas constant `R = 8.3 J//mol-K`.

Answer

`4.2J//cal`

Explanation

As `C_(P) - C_(V) = R = 8.3 J//mol-K`
`1.97 = 8.3J`.
`:.` Mechanical equivalent of heat is
`(8.3J)/(1.97cal) = 4.2 J//cal`.