R1.2.1 Average Bond Enthalpy Calculations [SL IB Chemistry]

If you know the energy required to break all the bonds in the reactants AND make all the bonds in the products you can work out the overall energy change for the reaction. Assume STP and this only works if everything involved is a gas. (Else the energy you put in may cause evaporation, boiling, hydrogen-bond breaking etc).

[nishitnath]

Hello Mr Thornley,
You have to be the best chemistry teacher on the bloody planet.
I've clarified so many of my doubts just going through your videos in less than an hour.
Man, you rock

[mango_tangy]

Hello Mr. Thornley, I have been watching your videos for over two years and I am starting Chem IB exams tomorrow. You are a life saver. Thank you so much for your help, and once exams are over, I will miss your amazing videos. Also, you remind me of Walter White. Your goatee just looks like him. Anyways, thank you.

[MrMysteryBanana]

Pro IB Chem teacher. The only IB video's on youtube that is cool. G-mod nerd level over 9000. this helps students remember and use all there senses.

[TheKemics]

Very concise and clear, if only all teachers could be like this!

[CrazyTomer]

"More makey than breakey" You make learning fun :)  Also Ib exams in 3

[ibchemvids]

Hey, this is my 25 question today from all over the world - i am happy to help.
1) Yes you can leave out the bonds that are broken then made - but people often mess this up - even though they know what they are doing - so be careful.
2) C triple C minus C single C = strength of 2 pi bonds

[zainashraf]

Amazing, very clear and easy to follow...thanks so much!

[nawedy]

Amazing review videos, like Khan academy but specific for the IB! Keep up the good work!

[Valzz]

Excellent. Love all your videos, I've seen so far.

[saraomran]

The way you explain lessons is just AMAZING it makes everything much easier and fun and exciting :') <3 <3 <3 

[xXxTamaraxXx]

If it weren't for you.. I don't even wanna think about it. Thank you so much!

[ibchemvids]

@vriffle I talked to the other 2 chem teachers here and they think that it is OK as written, and that dividing the delta H by the relevant coefficient would give you the value for that species - I probably should have mentioned that !

[ibchemvids]

Hey, Is this a trick - are you actually in MY class?! ;)

[borntobeme]

Thank you! Finally! My teacher taught me a method but it was so confusing lol. Ty

[elwynbrooks]

How come you're breaking and forming all of the bonds in the last example? The C-H bond is just reformed in the products, so can't you just leave that out of the equation? Will it still work? And I guess I would have to know the mechanism for the reaction, but why does the triple bond between the two C's break completely, only to reform a single bond? Can't it get rid of the pi bonds and call it a day? Is there a way to calculate that?

(Sorry for all the questions!)

[elenywohlner]

To find delta H you said you must add up all the numbers, but how can you tell when to do that or use the equation of delta H = sum of all products - sum of all reactants?

[lordunicorn]

So I am solving some questions about average bond enthalpies from past papers, and I am following the exact method but the answers I am getting are different from that of the markscheme, is it Because they changed the values in the data booklet? And btw it is now table 11

[xxCCBBxx]

Woot, this just saved my ass for tomorrow.

[rodrigom.alonso]

Need to Correct, Now bond enthalpies stand at table 11 in the formula booklet.

Thank you as always.

[rikku]

I like when you were saying *my teacher says do it different way!* funnaayy :D