Answer
$-170 \text{ J/g}$
$-20.\text{ kJ/mol}$
Work Step by Step
$\Delta H = q$ (because pressure is constant)
$\Delta H = mc\Delta T$
$\Delta H = (125+10.5)*4.18*(21.1-24.2)=-1.8$ kJ
$\frac{-1.8 kJ}{10.5\text{ grams}}=-170 \text{ J/g}$
$\frac{-1.8 kJ}{10.5\text{ grams}}*\frac{119 \text{ grams}}{1\text{ mol }}=-20.\text{ kJ/mol}$