(a) If a chemical equation is multiplied by some factor, then $\Delta$$H$ is also multiplied by the same factor. (a) If a chemcial equation is reversed, $\Delta$$H$ also changes sign.
Work Step by Step
These relationships hold because enthalpy is a state function. Twice as much energy is transferred in twice the quantity of reactants and products. Reversing a reaction switches the initial and final states, which means the direction of heat flow is reversed.