AS Chemistry- helping each other out!

Did they not give the bond enthalpy for C-H & C-C bonds??
p.s. What is the answer they obtained?

Na they gave all of it. It's just the ethene bit I don't understand.
C-H = 413
C-C= 347
C=C = 612
H-H= 436

The answer is -125KJmol^-1

I don't understand the bonds in the ethene.

It says answer: [612+436]-[(2x413)+347) =-125KJ mol^-1

Na they gave all of it. It's just the ethene bit I don't understand.
C-H = 413
C-C= 347
C=C = 612
H-H= 436

The answer is -125KJmol^-1

I don't understand the bonds in the ethene.

It says answer: [612+436]-[(2x413)+347) =-125KJ mol^-1

Bonds broken:
1 C=C (612)
4 C-H (4 x 413 = 1652)
1 H-H (436)
The total is when you add them together = 2700

Bonds made:
1 C-C (347)
6 C-H (6 x 413 = 2478)
Total = 2825

When finding the enthalpy change you use like you said 'Bond broken - Bonds made'
Therefore in this case we have to do the following: 2700 - 2825 = -125kJmol^-1

(every value is in kJmol^-1)
Hope that helped

hey everyone
need help with this question: what oxidation number does nitrogen have in HCN?
I kind of understand that it is probably -5 if the ON of C is +4. However, there are different answers in the internet

Helloooo, I wonder if somebody can help with something I came across in a textbook and am really confused.
So the question was to draw the structure of 1,1-dimethyl-3-ethylcyclohexane, which I thought was simple enough, except this is the answer they put in the book ... ( see attached picture below)

I just don't see how the ethyl group can be on the carbon which I have labelled 2 ( the labels in red were done by me, they weren't in the book) when it says "3-ethyl"... the book even says, "Add two methyl groups to one carbon atom, which becomes carbon atom 1. Then add an ethyl group to carbon atom 3". But to me that ethyl group is on carbon 2! Am I missing something?

I hope my question makes sense I know its a bit long winded haha... I just don't get it!!!!!!!!!

You've added two methyl groups on carbon-1 where it says 3-ethyl, you can count clockwise or anticlockwise, so you put the ethyl group on the third carbon from carbon-1 clock or anticlockwise.

Helloooo, I wonder if somebody can help with something I came across in a textbook and am really confused.
So the question was to draw the structure of 1,1-dimethyl-3-ethylcyclohexane, which I thought was simple enough, except this is the answer they put in the book ... ( see attached picture below)

I just don't see how the ethyl group can be on the carbon which I have labelled 2 ( the labels in red were done by me, they weren't in the book) when it says "3-ethyl"... the book even says, "Add two methyl groups to one carbon atom, which becomes carbon atom 1. Then add an ethyl group to carbon atom 3". But to me that ethyl group is on carbon 2! Am I missing something?

I hope my question makes sense I know its a bit long winded haha... I just don't get it!!!!!!!!!

But in the picture the two groups are on carbons next to each other whatever way you count the carbons...

They've probably made a mistake, I wouldn't read too much into it.


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Sounds like the textbook's made a mistake...

Do you think so? That crossed my mind but I just didn't think it was possible, I've got every other question right /understood my mistake, so yeah you're probably right about over thinking it...I tend to do that haha. Thank you!!

Hey guys,
I do OCR A.
I was just wondering why my teacher stressed on the importance of the 5 ions (Carbonate, Nitrate, Sulphate, Hydroxide and Ammonium)?
Why do we NEED to learn their formula and names?

Need some help with an enthalpy change question

Calculate the enthalpy changes of reaction for each of the following reaction

a). C2H4(g) + H2(g) ----> C2H6(g)

Right so it gives you a ton of values. So since they are in the gas state it is Sum of bonds broken - Sum of bonds made.

There is a C=C double bond which is 612Kjmol^-1
But it says there is one H-H bond that gives the 436Kjmol^-1
I don't really understand that bit isn't there 4 C-H bonds? Can someone explain this. I get the rest of the question apart from this bit.

Thanks