Endothermic and endothermic enthalpy changes.

Watch
MattHorwood
Badges: 6
Rep:
?
#1
Report Thread starter 2 years ago
#1
Can someone please explain why, when calculating enthalpy change of an exothermic reaction, the average bond enthalpy of he products is higher so a negative value is achieved. I thought exothermic reactions lost energy to the surroundings so how do they end up with a higher average bond enthalpy on the product side if energy is lost? This feels like a dumb question from an A-level student but I just don’t quite understand.
0
reply
charco
Badges: 17
Rep:
?
#2
Report 2 years ago
#2
(Original post by MattHorwood)
Can someone please explain why, when calculating enthalpy change of an exothermic reaction, the average bond enthalpy of he products is higher so a negative value is achieved. I thought exothermic reactions lost energy to the surroundings so how do they end up with a higher average bond enthalpy on the product side if energy is lost? This feels like a dumb question from an A-level student but I just don’t quite understand.
There are two different forms of energy being discussed:

1. Chemical potential energy
2. Heat (kinetic) energy

An exothermic reaction changes chemical potential energy into heat energy.

The more stable a system is the less chemical potential energy it possesses.

Strong bonds are more stable and have less chemical potential energy.

Hence in a chemical reaction bond breaking of the reactants involves endothermic change as heat energy is converted into CPE, and bond formation of the products involves change from CPE to kinetic energy.
1
reply
MattHorwood
Badges: 6
Rep:
?
#3
Report Thread starter 2 years ago
#3
(Original post by charco)
There are two different forms of energy being discussed:

1. Chemical potential energy
2. Heat (kinetic) energy

An exothermic reaction changes chemical potential energy into heat energy.

The more stable a system is the less chemical potential energy it possesses.

Strong bonds are more stable and have less chemical potential energy.

Hence in a chemical reaction bond breaking of the reactants involves endothermic change as heat energy is converted into CPE, and bond formation of the products involves change from CPE to kinetic energy.
Oh I finally get it. Thank you so much!
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Do you have the space and resources you need to succeed in home learning?

Yes I have everything I need (92)
65.25%
I don't have everything I need (49)
34.75%

Watched Threads

View All
Latest
My Feed