R1.2.2 Hess's Law [SL IB Chemistry]

Determine the enthalpy change of a reaction that is the sum of two or three reactions with known enthalpy changes. You don't need to know Hess's Law (!) but you need to be able to use it three ways. The law allows you to work out delta H for reactions, given the delta H for other reactions. You can even work out delta H for reactions that cannot occur. Look up Hess's Law you lazy bum!

[BestofBuzzYT]

Been 8 years and there is still no better video than this on Hess law.

[Sleekflight]

Sir Richard, saviour of IB chem students everywhere!

[HardikKundalwal]

I have final exams in 2 days, and as usual you're the hero. (Just completed watching videos of topics which are troubling me, chemistry and chill 😄🤠)

[ee]

IB exam in 5 hours and gonna be dubs thanks to ur videos over the past 2 years 🤟

[TadanoCandy]

I am in chem class right now, I dont get anything but I get 100%s in tests thanks to your videos.

[한명규-em]

Thank you so much for all your videos. I used to get 2 and 3 in SL chem before, but when I found you on youtube, i am now getting 6 and

[turbothrottletrouble]

you have, officially, saved my life.

[elwynbrooks]

Hey, for 6:42, the combustion of ethene equation, I can't balance it so that it goes to 2CO2 + 3H2O.

I'm looking at:

C2H4 + 3O2 --> 2CO2 + 2H2O, but you have down 3H2O instead. The three waters is balanced for combustion of ethanol, but I can't balance it for the combustion of ethene. What am I missing here?

I'm getting the right relationships (tried it using the equations method) for the deltaH's, but I'm not sure what/how to put down that third equation in the cycle. Help?

[thingy]

Thanks for saving my life Mr. Thornley, id love to play some cs with you just to hang about. Thanks for everything!

[Lunibruniful]

youre a boss. thank you so much I'm gonna pass my midterm today!

[tongeli]

Oh my ! If i pass my Chemistry finals it's all because of you Mr. Thornley!

[vshlhs]

Thank you so much. I missed a class day and didn't understand anything at all! but this helps so much! thanks!

[ibchemvids]

and if you fail we can blame your teacher - hehehe!

[ibchemvids]

@ridhajawad You need all 3 ways - equations, cycle and energy diagram
Recently they marked down papers that did not use a cycle.
RT

[ibchemvids]

the purple arrow is a little too far left-- you also need to bring the H2O down - then it works

[ibchemvids]

yup, make sure you can use your own calculator! If not break the calculation up into smaller bits and be clear on the exam with your working for partial credit.

[ridhajawad]

hi! do we have to be able to solve through the energy cycle way? I only know how to do it the first way, should I learn the other way as well..

[codosacho]

I wanna ask what is the difference between the heat formation of a compound and its heat content

[user]

awesome videos!
But in the medium cycle one. the (1/2O2 / -2/3O2 etc.) do we have to know the meaning of them or how to draw them on the cycle?

[omcnfbct]

Same and I did exactly what he did as well.
I think there was just a simple problem of summation in the video.