Question

1. A reaction has ΔrH=+100 kJ⋅mol-1. Is the reaction exothermic or endothermic?

Answer 1

nswer:

E

a

=

40 kJ⋅mol

-1

Explanation:

Here's a schematic progress of reaction diagram for an endothermic reaction.

ProgReaction

ProgReaction

(Adapted from BBC)

We see that

Δ

‡

H

(

fwd

)

(from reactants to transition state) is

140 kJ⋅mol

-1

.

We also see that

Δ

rxn

H

(from reactants to products is

100 kJ⋅mol

-1

.

Thus,

Δ

‡

H

(

rev

)

(products to transition state) must be

Δ

‡

H

(

rev

)

=

140 kJ⋅mol

-1

−

100 kJ⋅mol

-1

=

40 kJ⋅mol

-1