Question

Identify a reason that chemical reactions release energy during the reaction process.

Select one:
a. forming bonds
b. breaking bonds
c. storing energy
d. overcoming activation energy

Answer 1

Answer:

option b

Explanation:

When the energy is released the process is called exothermic reaction. This happens when the bonds are broken in the reactants and the system release energy.

Answer 2

Answer:

a. forming bonds

Explanation:

The energy required to break a bond is endothermic that is energy is absorbed to break a bond.

The energy is released in the formation of a bond that is energy is released when a bond is formed.

The formula to find the ∆H of the reaction is  

∆H (reaction) = ∆H (bonds Broken) - ∆H (bonds formed)

For example  

$N_2+3H_2< >2NH_3$

$N_2$ contains one N≡N triple bond (Bond breaking 946 KJ per mol)

$H_2$ contains a single H-H bond (bond breaking 436 KJ per mol)

$NH_3$ contains 3, N - H single bonds(389 KJ per mol)

So ∆H (bonds broken) = 946 + (3 × 436) = 2254KJ

∆H (Bonds formed ) = (2 × 3 × 389) = 2334KJ

So

∆H (reaction) = 2254 KJ - 2334 KJ

= - 80KJ and the reaction is Exothermic

In this example we see energy required to break the bond is lesser than energy released in forming the bond.