Question

$1 \,kg$ of boiling water at $100^{\circ} C$ is dropped into Indian ocean, the temperature of which is $27^{\circ} C$. Calculate entropy change of the universe $\left( JK ^{-1}\right)$
[specific heat of water $=4.2 \times 10^{3} J kg ^{-1}$,
$\left.\log \left(\frac{298}{373}\right)=0.0975\right]$

Answer 1

Amount of heat lost by $1 \,kg\, H _{2} O = m s \Delta T$
$=315000$ Joule
$\therefore $ This heat is absorbed by ocean hence entropy of ocean increases $=\frac{ dq }{ T }=1050 \,JK ^{-1}$
And entropy decrease of $1 \,kg$ of boiled $H _{2} O$
$=-941.85 \,J$
$\therefore \Delta S _{\text {universe }}=108.15 \,JK ^{-1}$