احسب $\Delta H_r^{\circ}$ للتفاعل $C_{(gra)} + \frac{1}{2}O_{2(g)} \rightarrow CO_{(g)}$ إذا علمت أن $C_{(gra)}+O_{2(g)}\rightarrow CO_{2(g)}$، $\Delta H_r^{\circ}=-394\ \text{kJ/mol}$ و $CO_{(g)}+\frac{1}{2}O_{2(g)}\rightarrow CO_{2(g)}$، $\Delta H_r^{\circ}=-283\ \text{kJ/mol}$