Question

Latent heat of vaporization of water is $538$ cal/g. During the conversion of $1$ g of water to steam, if the external work done is $168$J, the increase in internal energy is :

• A. $638cal$
• B. $538cal$
• C. $498cal$
• D. $80cal$

Answer 1

The correct option is C $498cal$

Total heat energy required $=$ change in internal energy + work done
Here, heat energy required is the latent heat of vaporization.
Change in internal energy$=538-168\left(0.239\right)=538-40.152=497.848cal$
( $1J$=$0.239cal$ )