Chapter 5, Problem 77E

In the early days of automobiles, illumination at night was provided by burning acetylene, ${\text{C}}_2{\text{H}}_2$. 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, ${\text{CaC}}_2$ :

${\text{CaC}}_2\left(s\right)+2{\text{H}}_2\text{O}\left(l\right)\to \text{Ca}{\left(\text{OH}\right)}_2\left(s\right)+{\text{C}}_2{\text{H}}_2\left(g\right)$.

Calculate the standard enthalpy of the reaction. The

$\Delta H_{\text{f}}^{°}$ of ${\text{CaC}}_2$ is −15.14 kcal/mol.