Question

How much energy is transferred when $1gm$ of boiling water at ${100}^{\circ }C$ cools to water at ${100}^{\circ }C$?

• A. $2255J/g$
• B. $2256J/g$
• C. $2257J/g$
• D. $2258J/g$

Answer 1

Answer: (C)

$2257J/g$

Whenever there is state change the temperature remains constant but still either energy is absorbed or released depending upon wheather heated or cooled.

The energy involved is called latent heat.

Here when water is condensed from boiling vapours to water at ${100}^{0}C$ the energy is released called Latent heat of vapourisation and for water on condensing water its Latent heat of vapourisation is equal to $2257J/gm$.

Hence energy released for $1gm$ on condensing to water is $2257J$.