Is this exothermic reaction truly endoenergetic?

In summary, the reaction I2 (g) + H2 --> 2HI has a negative enthalpy change of -10 kJ/mol, indicating an exothermic reaction. The energy involved in breaking bonds in H2 and I2 is greater than the energy released in forming bonds in HI, which is characteristic of an endothermic reaction. This is supported by the bond enthalpies, which show that the energy associated with bonds being made is greater than that of the bonds being broken. Therefore, the statement in the book is incorrect and the reaction is indeed exothermic. Additionally, there may be a typo in the book as the calculated enthalpy change is -9 kJ/mol, not -10 kJ
  • #1
PPonte
I2 (g) + H2 --> 2HI dH = - 10 kJ/mol

In this reaction the energy involved in the breaking of bonds in H2 and I2 is great in quantity than the energy released in the formation of bonds in HI.

My book says that this sentence is true, but I do not agree.
The breaking of bonds is an endoenergetic process and the formation of bonds is an exoenergetic process. If the reaction is exoenergetic this means that the exoenergetic process involves more energy than the endoenergetic process.
We can see it by other way. If the energy involved in the breaking of bonds in H2 and I2 is great in quantity than the energy released in the formation of bonds in HI this means that the reactional systhem obtained energy and thus the enthalpy of the products is higher than the enthalpy of the reactants, which is an caractheristic of an endoenergetic reaction and not of an exoenergetic reaction.
Am I right?
 
Physics news on Phys.org
  • #2
If the enthalpy change is negative, this indicated an exothermic reaction, energy is being release into the surroundinga. The energy associated with bonds being made is greater than that of the bonds being broken.
 
  • #3
Exactly! I think I am right.
 
  • #4
According to my data the bond enthalpies are as follows:
[tex]H-H = 436 kJ\cdot mol^{-1}[/tex]
[tex]I-I = 151 kJ\cdot mol^{-1}[/tex]
[tex]H-I = 298 kJ\cdot mol^{-1}[/tex]
This gives the enthalpy of broken bonds to be 587 and bonds made of 596 which means:
[tex]\Delta H = -9 kJ\cdot mol^{-1} [/tex]
Which would agree with your comments. It seems your book has a typo!
 
  • #5
It seems so. But has less typos than the other books I had.
Thank you very much for your help!
 

1. What is an exothermic reaction?

An exothermic reaction is a chemical reaction in which energy is released in the form of heat. This means that the reactants have a higher potential energy than the products, and the excess energy is released as heat.

2. How can you tell if a reaction is exothermic?

If you feel heat being given off during the reaction, it is likely an exothermic reaction. You can also measure the temperature change of the surroundings, as exothermic reactions typically result in an increase in temperature.

3. What are some examples of exothermic reactions?

Some common examples of exothermic reactions include combustion (such as burning wood or fuels), neutralization reactions (when an acid and a base react to form salt and water), and oxidation reactions (such as rusting of iron).

4. What is the difference between an exothermic and an endothermic reaction?

The main difference between exothermic and endothermic reactions is the direction of energy flow. In exothermic reactions, energy is released from the system into the surroundings, while in endothermic reactions, energy is absorbed from the surroundings into the system.

5. How are exothermic reactions used in everyday life?

Exothermic reactions are used in many everyday applications, such as cooking (where heat from burning fuels is used to cook food), hand warmers (which use an exothermic reaction to release heat), and self-heating cans (which use an exothermic reaction to heat up the contents when activated).

Similar threads

  • Biology and Chemistry Homework Help
Replies
6
Views
2K
  • Biology and Chemistry Homework Help
Replies
2
Views
1K
  • Biology and Chemistry Homework Help
Replies
2
Views
2K
  • Biology and Chemistry Homework Help
Replies
3
Views
2K
  • Biology and Chemistry Homework Help
Replies
4
Views
1K
  • Biology and Chemistry Homework Help
Replies
2
Views
1K
  • Biology and Chemistry Homework Help
Replies
3
Views
5K
  • Biology and Chemistry Homework Help
Replies
4
Views
2K
  • Biology and Chemistry Homework Help
Replies
1
Views
3K
  • Biology and Chemistry Homework Help
Replies
1
Views
1K
Back
Top