# Question #b773e

Apr 11, 2017

$\Delta H \text{of reaction"= "-121.2kJ/mol}$

#### Explanation:

$2 C O + {O}_{2} = 2 C {O}_{2}$

$\Delta H \text{of reaction" = DeltaH_f^@ of "product(s)" - DeltaH_f^@ of "reactants}$

The product in this reaction is CO

$\Delta {H}_{f}^{\circ}$ of CO is -253.7KJ/mol

The reactants in this reaction are ${O}_{2}$ and $C {O}_{2}$

But the $\Delta {H}_{f}^{\circ}$ of ${O}_{2}$ is not there

The $\Delta {H}_{f}^{\circ}$ of all elements is 0kJ/mol

So the $\Delta {H}_{f}^{\circ}$ of ${O}_{2}$ is
0kJ/mol

The combined $\Delta {H}_{f}^{\circ}$of products should be multiplied by their coefficients .

-253.7KJ/mol 2 + 0kJ/mol1 = -507.4kJ/mol

$\Delta {H}_{f}^{\circ}$ of products

$C {O}_{2}$ = -314.3kJ/mol

And remember also multiply by the coefficient

-314.3kJ/mol* 2 = -628.6

Plug the values in the equation

$\Delta H \text{of reaction" = DeltaH_f^@ of "product(s)" - DeltaH_f^@ of "reactants}$

$\text{-628.6kJ/mol - (-507.4kJ/mol)}$

$\Delta H \text{of reaction"= "-121.2kJ/mol}$