[sabre2th1]

For Q1b), I know that it cannot be A or B, so we are left with C or D.. Is C considered as a displacement reactions or not? Why is the answer D? I mean the SO₄ doesn't displace anything?

How do you do Q10? I just calculated the moles of each compounds, and found that D is the only one that has a different value so I chose that as my answer, but the correct answer is C. I know it says ions, so its something related to that, but I am unsure of how to progress..

Q11), I know C and D are correct, so we are left with A and B.. I know A is correct as alkenes cannot rotate, but isn't B correct also?

Thanks

[KLAV]

Answers: 1D 2C(?) 3B

Edit: Oh you gave us the answers.. oops.

1. Mg displaces the Cu as it's more reactive. Read up on the reactivity series and displacement reactions.

2. You're right to work out the number of moles. But you then have to work out how each was made. ie
Na+ + Cl- --> NaCl
Mg2+ + 2Cl- --> MgCl2

You then work out the number of moles of the Na+/Cl- needed. (The ratio is 1:1 so it is 1x10^-3 for each)

For Mg/Cl (for option D) you end up with 6.665x10^5 for Mg and double that (due to the mole ration) for Cl: 1.33x10^-3

Now what you do is add the number of moles on the reactant side together and multiply by avagadro's number. This will give you around 1.2x10^21 for options A B and D. It's a little higher for C as there going to be more molecules due to the additional volume.

3 C=C is shorter than 2xC-C. You probably don't need to know the specifics but I think it's because C=C isn't made of 2 SIGMA bonds, instead it is made of 1 sigma and 1 pi, which when added up in terms of bond energy does not equal 2x sigma.

[sabre2th1]

(Original post by KLAV)
...

AH! I realise my mistake in the first one.. as for the second one, I'm still confused ..

Regarding the third one; so C=C bonds are less than twice as strong as C-C bonds right?

Thanks

[Pride]

(Original post by sabre2th1)
AH! I realise my mistake in the first one.. as for the second one, I'm still confused ..

Regarding the third one; so C=C bonds are less than twice as strong as C-C bonds right?

Thanks

yep exactly. Remember what you've learnt about the C=C double bond? It consists of a sigma bond and a weaker pi-bond. C-C single bonds are just a sigma.

[sabre2th1]

(Original post by Pride)
yep exactly. Remember what you've learnt about the C=C double bond? It consists of a sigma bond and a weaker pi-bond. C-C single bonds are just a sigma.

Ah I see! Cheers mate!

[Pride]

(Original post by sabre2th1)
Ah I see! Cheers mate!

ahh great

[sabre2th1]

(Original post by Pride)
ahh great

I posted a thread, and it didn't appear for some reason, so I rewrote it and decided to repost it. Then I noticed it said the moderator has to approve it.. Is this only an issue with my account or is it a new rule across TSR? (can't post a thread and ask the mods lol :P)

[Pride]

(Original post by sabre2th1)
I posted a thread, and it didn't appear for some reason, so I rewrote it and decided to repost it. Then I noticed it said the moderator has to approve it.. Is this only an issue with my account or is it a new rule across TSR? (can't post a thread and ask the mods lol :P)

I'm not entirely sure. It may be because it was a repeat, or because you wrote another thread too soon after the first.

[EierVonSatan]

It looks like the mods are filtering certain threads for some reason was it called ''multiple choice questions'' or something? I can see the title but not the thread.

[sconter]

d c b

[sabre2th1]

(Original post by Pride)
I'm not entirely sure. It may be because it was a repeat, or because you wrote another thread too soon after the first.

The first one I wrote didn't show up so I got confused and rewrote it.. I don't think its about the timing because the last thread I posted (before today's first one) was last night

(Original post by EierVonSatan)
It looks like the mods are filtering certain threads for some reason was it called ''multiple choice questions'' or something? I can see the title but not the thread.

Yeah that's it.. I can't see it? Maybe I can't see it because you have more privileges than me on here :P

[EierVonSatan]

(Original post by sabre2th1)
Yeah that's it.. I can't see it? Maybe I can't see it because you have more privileges than me on here :P

I could only see it for a short while, I'm sure they'll get around to approving it soon

Normally it's only brand new users that post links or people using the anon function in H&R that have to be pre-approved, but they've made a few changes/upgrades to how it works.

[sabre2th1]

(Original post by EierVonSatan)
I could only see it for a short while, I'm sure they'll get around to approving it soon

Normally it's only brand new users that post links or people using the anon function in H&R that have to be pre-approved, but they've made a few changes/upgrades to how it works.

There have been changes to prevent people discussing exam answers (a mod told me).. :P

[EierVonSatan]

(Original post by sabre2th1)
There have been changes to prevent people discussing exam answers (a mod told me).. :P

It's more than just that but that's certainly part of it (I've been a mod)

[sabre2th1]

(Original post by EierVonSatan)
It's more than just that but that's certainly part of it (I've been a mod)

I see aha