Question

A student made a sketch of a potential energy diagram to represent an exothermic reaction.

Answer 1

Answer:

Since heat is released for

C

3

H

8

(

g

)

+

5

O

2

(

g

)

→

3

CO

2

(

g

)

+

4

H

2

O

(

g

)

+

2219.9

kJ

,

we say that

Δ

H

∘

C

=

−

2219.9 kJ/mol propane

. We approximate that this is the change in potential energy for the reactants going to the products.

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The above is for an endothermic reaction.

A certain feature of combustion reactions suggests that you should draw the diagram DIFFERENTLY from what you see above. How should the energy of the products compare with that of the reactants for combustion reactions?