Answer
a) $-584.8 \text{ kJmol}^{-1}$; exothermic
b) $-44.2 \text{ kJmol}^{-1}$; exothermic
c) $-422.8 \text{ kJmol}^{-1}$; exothermic
Work Step by Step
The $\Delta H^{\circ}_{f}$ value can be taken by subtracting initial enthalpy from the final using the given values,
$\Delta H^{\circ}_{f} = H^{\circ}_{f} Initial-H^{\circ}_{f}final$
When the sign of the enthalpy change is negative reaction is exothermic as energy is released, when sign is positive reaction is endothermic as energy is absorbed
a) $-584.8 \text{ kJmol}^{-1}$; exothermic
b) $-44.2 \text{ kJmol}^{-1}$; exothermic
c) $-422.8 \text{ kJmol}^{-1}$; exothermic
