Question

The molar heat capacity of water at constant pressure, $C$, is $75\, JK ^{-1}\, mol ^{-1}$. When $1.0\, KJ$ of heat is supplied to $100\, g$ of water which is free to expand, the increase in temperature of water is :

• A. 6.6 K
• B. 1.2 K
• C. 2.4 K
• D. 4.8 K

Answer 1

Answer: (C)

2.4 K

Answer 2

$Q = 1\, kJ = 1000\, J$
$m = 100 \, g = \frac{100 \, g}{18 \, g\, mol^{-1}} = 5.55 \, mol$
$Q = mC . \Delta t$
$\Delta t = \frac{Q}{m.C.} = \frac{1000 \, J}{5.55 \, mol \times 75 \,JK^{-1} mol^{-1}} = 2.4\, K$