Bond Enthalpies
Moderators: Chem_Mod, Chem_Admin
-
- Posts: 22
- Joined: Fri Sep 29, 2017 7:06 am
Bond Enthalpies
In lecture today, we learned how to use bond enthalpy to calculate ΔH. Just to clarify, does it mean that ΔH= ∑bond broke - ∑bond formed?
-
- Posts: 51
- Joined: Fri Sep 29, 2017 7:07 am
Re: Bond Enthalpies
Yes! You just add the energy required with the energy released, but the released energy would have a negative value. So its the energy required minus energy released.
-
- Posts: 30
- Joined: Thu Jul 13, 2017 3:00 am
Re: Bond Enthalpies
Yes, ΔH= (energy needed to break the reactant bonds) - (energy released by forming the product bonds) gives the change in enthalpy for the reaction
-
- Posts: 51
- Joined: Thu Jul 27, 2017 3:01 am
- Been upvoted: 1 time
Re: Bond Enthalpies
That's correct! ΔHRXN is equal to Energy required to break bonds (positive values) minus energy required to form bonds (or using addition and making sure to include that the values are negative.)
The example in class was C=C (+612 kJ/mol), H-Br (+366 kJ/mol) -> C-C (-348 kJ/mol), C-H (-412 kJ/mol), C-Br (-276 kJ/mol). ΔH = 978 - 1036 = -58 kJ (exothermic).
The example in class was C=C (+612 kJ/mol), H-Br (+366 kJ/mol) -> C-C (-348 kJ/mol), C-H (-412 kJ/mol), C-Br (-276 kJ/mol). ΔH = 978 - 1036 = -58 kJ (exothermic).
-
- Posts: 50
- Joined: Thu Jul 13, 2017 3:00 am
Re: Bond Enthalpies
The change in enthalpy is just adding the energy released when a bond is broken (a positive value) and energy needed to form the bond (a negative value). Or if it helps you to remember, you can think of it as the difference between energy released when the bond is broken and the energy required to form the new bond.
-
- Posts: 70
- Joined: Fri Sep 29, 2017 7:04 am
Re: Bond Enthalpies
Yes and no. You are just adding the values together. The values of energy required are always positive and the values of energy released are negative. So just add the positive and negative values.
Who is online
Users browsing this forum: No registered users and 11 guests