Question

100 g of water heated from ${30}^0$C to${50}^0$ C Ignoring the slight expansion of the water, the change in its internal energy is (specific heat of water is 4184 J/kg/K):

• A. 84 kJ
• B. 2.1 kJ
• C. 4.2 kJ
• D. 8.4 kJ

Answer 1

The correct option is D 8.4 kJ

when $m=100g$ of water (Specific heat, $S=41874k{g}^{-1}{K}^{-1}$) is heated

$=0.1kg$

by a temperature $\Delta T={50}^{o}c-{30}^{o}c=20k$, the change in internal energy is =

$du=mS\Delta T=0.1\times 4184\times 20$

$=8368J\simeq 8.4kJ$