Question

How much heat energy is gained when $5kg$ of water at ${20}^{\circ }C$ is brought to its boiling point?
$(\text{Specific heat of water}=4.2kJk{g}^{-1}{c}^{-1})$

• A. $1680kJ$
• B. $1700kJ$
• C. $1720kJ$
• D. $1740kJ$

Answer 1

The correct option is A

$1680kJ$

Given:
Mass of water, $m=5kg$
Specific heat of water, $c=4.2kJk{g}^{-1}{}^{\circ }{C}^{-1}$
Rise in temperature of water $\Delta \theta =100-20={80}^{\circ }C$

Heat gained is given by:
$Q=mc\Delta \theta$
$Q=5\times 4.2\times {10}^3\times 80J$
$Q=1680\times {10}^{3}J=1680kJ$