heats

you to determine heats of reaction by combining multiple reactions with known enthalpy changes. When to Use Hess’s Law When direct enthalpy data isn’t available. When reactions can be broken into steps with known heats. To calculate heats for complex reactions via

m of individual heats, weighted by their proportions. Example Calculation: If: ΔH A = -500 kJ ΔH B = -300 kJ and the mixture contains 2 mol of X and 3 mol of Y, then: Expected total heat: ΔH total = (2 mol × ΔH A ) + (3 mol × ΔH B ) = (2 × -500) + (3 × -300) = -1000 - 900 =