140 grams of nitrogen absorbs 60 calories of heat without change in volume. If the temperature increases from `27^(@)C` to `30^(@)C` while doing so then what is the value of molar heat capacity ?

Options

A. `2 cal K^(-1) mol^(-1)`
B. `4 cal K^(-1) mol^(-1)`
C. `5 cal K^(-1) mol^(-1)`
D. `20 cal K^(-1) mol^(-1)`

Answer

B

Explanation

As the gas absorbs heat without change in volume
`:. W=0" "( :' V=0)`
Heat absorbed, `q=60` calories
Sicne `Delta E =q+W =60 +0=60cal`
`C_(v)(` heat capacity at constant volume)
`=(DeltaE)/(T_(2)-T_(1))=(30)/(303-330)=20 cal K^(-1)`
Since moles of `N_(2)` gas given `=(140)/(28)=5`
`:. ` Molar heat capacity `=(20cal)/(5)K^(-1)`
`=4 cal K^(-1) mol^(-1)`