Question

how is total reaction energy calculated?

a ) reactant bond energy + product bond energy
b ) product bond energy x reactant bond energy
c ) reactant bond energy - product bond energy
d ) product bond energy ÷ reactant bond energy

Answer 1

The total reaction energy is calculated based on the difference between the bond energies of the reactants and the bond energies of the products. Thus, the correct way to determine the total reaction energy is:

c ) reactant bond energy - product bond energy

In a chemical reaction, bonds are broken in the reactants, which requires energy, and bonds are formed in the products, which releases energy. The bond energy is a measure of the strength of a chemical bond and is usually reported in units of kilojoules per mole (kJ/mol). The total reaction energy (also called the change in enthalpy, ΔH) is the net amount of energy absorbed or released during the reaction.

If the reactants have higher bond energy than the products, the excess energy is released to the surroundings, and the reaction is exothermic (ΔH is negative). If the reactants have lower bond energy than the products, energy is absorbed from the surroundings, and the reaction is endothermic (ΔH is positive).