Suppose reaction A involves the breaking of bonds and 75 J of energy, reaction B involves the breaking of bonds and 40 J of energy, and reaction C involves the making of bonds and 125 J of energy
What is the overall A + B + C reaction energy? Is this an exothermic or an endothermic reaction? Explain.
In making bonds, the total energy release was 125 J. This is more than the energy
supplied to break bonds, 75 J + 40 J = 115 J. Overall in this reaction, bonds are made and
net energy is supplied by the chemical system to the outside. This is an exothermic reaction,
because energy of 10 J [= 125 J - 115 J] can be extracted from the system when the
reaction occurs.
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