Question

The energies of the bonds broken in a certain reaction are greater than the energies of the bonds formed. Which one of the following statements about this reaction must be true?
a. The reaction is endothermic.
b. The reaction is exothermic.
c. The reaction is spontaneous.
d. The reaction is non-spontaneous.

Answer 1

Answer:

a. The reaction is endothermic.

Explanation:

The heat involved in a chemical reaction is given by the enthalpy change (ΔH), which is equal to the balance between the chemical bonds that are broken (release energy) and the chemical bonds that are formed (need energy):

ΔH ≅ bonds broken - bonds formed

If broken bonds > bonds formed ⇒ ΔH > 0 ⇒ endothermic reaction

Therefore, the reaction is endothermic (it requires energy).