The heat change $\Delta H$ for the reaction $2CO + O_2 \to 2CO_2; \Delta H = -135 \ kcal$ is called

Given $C + O_2 \rightarrow CO_2$ : $\Delta H = -x \ kJ$ and $2CO + O_2 \rightarrow 2CO_2$ : $\Delta H^\circ = -y \ kJ$,find the enthalpy of formation of carbon monoxide.

$H_{2(g)} + \frac{1}{2}O_{2(g)} \to H_2O_{(l)}$; $\Delta H$ at $298 \ K = -285.8 \ kJ$. The molar enthalpy of vaporization of water at $1 \ atm$ and $25^{\circ}C$ is $44 \ kJ$. The standard enthalpy of formation of $1 \ mole$ of water vapor at $25^{\circ}C$ is $...... \ kJ$. (in $.8$)

The correct relationship between heat of fusion $(\Delta H_{fus})$,heat of vaporization $(\Delta H_{vap})$,and heat of sublimation $(\Delta H_{sub})$ is:

Which of the following statements is correct for the enthalpy of combustion?

Explain the change in enthalpy related to a chemical reaction.