• # question_answer 27) Calculate the standard enthalpy of formation of$C{{H}_{3}}OH(l)$from the following data: $C{{H}_{3}}OH(l)+\frac{3}{2}{{O}_{2}}(g)\to C{{O}_{2}}(g)+2{{H}_{2}}O(l);$ ${{\Delta }_{r}}{{H}^{{}^\circ }}=-726kJmo{{l}^{-1}}$ $C(s)+{{O}_{2}}(g)\to C{{O}_{2}}(g);$ ${{\Delta }_{c}}{{H}^{{}^\circ }}=-393kJ\,mo{{l}^{-1}}$ ${{H}_{2}}(s)+\frac{1}{2}{{O}_{2}}(g)\to H{{O}_{2}}(l);$ ${{\Delta }_{f}}{{H}^{{}^\circ }}=-286kJ\,mo{{l}^{-1}}$

The required equation is: $C(s)+2{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\to C{{H}_{3}}OH(l)$ The given equations can be rearranged as: (i) $C{{O}_{2}}(g)+2{{H}_{2}}O(l)\to C{{H}_{3}}OH(l)+\frac{3}{2}{{O}_{2}}(g);$ ${{\Delta }_{r}}{{H}^{{}^\circ }}=726kJmo{{l}^{-1}}$ (ii) $C(s)+{{O}_{2}}(g)\to C{{O}_{2}}(g);$ ${{\Delta }_{c}}{{H}^{{}^\circ }}=-393kJ\,mo{{l}^{-1}}$ (iii) $2{{H}_{2}}(g)+{{O}_{2}}(g)\to 2{{H}_{2}}O(l);$ ${{\Delta }_{f}}{{H}^{{}^\circ }}=-286\times 2kJmo{{l}^{-1}}$ $\frac{On\,adding,}{\frac{C(s)+2{{H}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\to C{{H}_{3}}OH(l);\Delta H=-239kJmo{{l}^{-1}}}{{}}}$