5.3 Exercise 39

In the early days of automobiles, illumination at night was provided by burning acetylene, C₂H₂. Though no longer used as auto headlamps, acetylene is still used as a source of light by some cave explorers. The acetylene is (was) prepared in the lamp by the reaction of water with calcium carbide, CaC₂:
$\text{CaC}_{2} \left(s\right) + 2 \text{H}_{2} \text{O} \left(l\right) \rightarrow \text{Ca} \left(\text{OH}\right)_{2} \left(s\right) + \text{C}_{2} \text{H}_{2} \left(g\right) .$
Calculate the standard enthalpy of the reaction. The $\Delta H_{\text{f}}^{\circ}$ of CaC₂ is −15.14 kcal/mol.