Answer
$-464.4\,kJ/mol$
Work Step by Step
$\Delta _{r}G^{\circ}=\Sigma n_{p}\Delta _{f}G^{\circ}(products)-\Sigma n_{r}\Delta _{f}G^{\circ}(reactants)$
$=[\Delta_{f}G^{\circ}(TiCl_{4},l)]-[\Delta_{f}G^{\circ}(TiCl_{2},s)+\Delta_{f}G^{\circ}(Cl_{2},g)]$
$\implies -272.8\,kJ/mol=(-737.2\,kJ/mol)-[\Delta_{f}G^{\circ}(TiCl_{2},s)+0]$
$\implies \Delta_{f}G^{\circ}(TiCl_{2},s)=(-737.2\,kJ/mol)+272.8\,kJ/mol$
$=-464.4\,kJ/mol$
