its component elements requires energy. Therefore, when the reaction runs in the opposite direction of the given direction, the enthalpy value takes the opposite sign. In addition, enthalpies are generally given for the equation with coefficients in simplest form. The formation of one mole of silver chloride releases -127.1 kJ/mol of energy. Therefore, if two moles of silver chloride are formed, it follows that the reaction releases 2(-127.1)kJ of energy. Producing two moles of silver chloride also requires doubling all of the coefficients of the equation. The enthalpy must be increased by the same factor as the coefficients.
Example:
Given the following reaction heats, find an equation describing the combustion of propane. Then find the total enthalpy change for the overall reaction.
