Question

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

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

Answer 1

The correct option is B $8.4$ $kJ$

$\Delta Q=\Delta U+\Delta W$

Since $\Delta W=0$, $\Delta Q=\Delta U$

$\Delta U=ms\Delta T=0.1\times 4.184\times 20=8.368kJ$