Question

if a chemical reaction is reversed, what happens to the enthalpy of the reaction? the sign of the enthalpy of the reaction reverses. the enthalpy of the reaction doubles. the enthalpy of the reaction is halved. the enthalpy of the reaction becomes zero.

Explanation:

Enthalpy is a state - function. When a chemical reaction is reversed, the heat change associated with the forward reaction has the same magnitude but the opposite sign for the reverse reaction. For example, if a forward reaction is exothermic (negative $\Delta H$), the reverse reaction is endothermic (positive $\Delta H$) with the same absolute value of $\Delta H$.

Answer:

The sign of the enthalpy of the reaction reverses.