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OCR B (Salters) F332 Tuesday 4th June 2013 Exam Discussion (Now Closed)

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Reply 820

super121

Original post by Davelittle

Q 1. Was 3,7-dimethyloct-3-ene

I put 2,6 because don't we have to use the lowest numbers. I think I forgot to write di :/

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Reply 821

Kathiye

Original post by Davelittle

No just NaCl, the 2:1 ratio of NaCl to Cl2 meant you had to half the moles of NaCl (not multiply the Mr by 2).

That should come out as the same thing, as long as they didn't use half of the moles AND multiply the Mr by 2, I think.

Reply 822

ActaNonVerba

Original post by super121

Didn't we have to work out the Mr of 2NaCl, apart from that I did the same steps

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no, moles = mass/Mr... the 2NaCl is significant because you divide the number of moles of NaCl by 2 to get I mole of Chlorine :smile:

Reply 823

Kathiye

Original post by juniorx

might lose 1 mark for accuracy?

Why would it? They didn't specify the number of significant figures, did they? Unless the actual answer is wrong. xD

Reply 824

abzy1234

Is the possible structure of the last section of Q1? Hope I remembered it well :tongue:

Reply 825

juniorx

Original post by abzy1234

Is the possible structure of the last section of Q1? Hope I remembered it well :tongue:

exactly i swear this can also be 2 ethyl 6 methyl hept 2 ene with the ethyl as that long bit at the top right?

Reply 826

abzy1234

Original post by super121

I don't think you multiply it by 2, as it'll cancel down anyway, as it's a 2:1 ratio I think.

If you got the final answer, regardless, you'll pick up the mark :smile:

Reply 827

abzy1234

Original post by juniorx

exactly i swear this can also be 2 ethyl 6 methyl hept 2 ene with the ethyl as that long bit at the top right?

I'm not too sure, as the top right part can be part of the main carbon chain. It's a complicated structure, so I'm sure they will have a variety of ways of answering it :smile:

Reply 828

super121

Original post by ActaNonVerba

no, moles = mass/Mr... the 2NaCl is significant because you divide the number of moles of NaCl by 2 to get I mole of Chlorine :smile:

I know that. I did the Mr of 2 NaCl (117 I think). (200000/117)/2 to get moles of Cl2 them multiplied that by 24.

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Reply 829

ambbs

Anyone else hate that last 6 mark question on the advance notice? Thought the paper was going alright up until I got to that question, I didn't have a clue!

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Reply 830

Kathiye

Original post by ambbs

Anyone else hate that last 6 mark question on the advance notice? Thought the paper was going alright up until I got to that question, I didn't have a clue!

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I quite liked it, actually. xD My main problem was trying not to copy the article...

Reply 831

Davelittle

Original post by juniorx

if this is wrong can someone tell me why it is wrong?

Well the longest carbon chain was 8, the double bond was between the third and the 4th carbon, there were methyl groups on the 3rd and 7th Carbon.

Therefore 3,7-dimethyloct-3-ene

Reply 832

Davelittle

Original post by super121

I know that. I did the Mr of 2 NaCl (117 I think). (200000/117)/2 to get moles of Cl2 them multiplied that by 24.

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Did you get 41025 or around that?

You didn't need to multiply the Mr of NaCl by 2!

Reply 833

abzy1234

Original post by ambbs

Anyone else hate that last 6 mark question on the advance notice? Thought the paper was going alright up until I got to that question, I didn't have a clue!

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I thought it was a nice 6-marker. The answers are mainly on the bottom right paragraph of page 3, with some of the equations already there. I talked about how N₂O can be broken down in the atmosphere by high frequency/energy UV radiation, giving the N₂O -> N₂ + O equation. Plus N₂O itself can react with existing oxygen radicals in the atmosphere, so that may break it down also...

I'm sure you would've picked up marks :smile:

Reply 834

super121

Original post by Davelittle

Did you get 41025 or around that?

You didn't need to multiply the Mr of NaCl by 2!

No, I got half of that so will probs just lose a mark as they have efc

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Reply 835

Jooost

what was the answer for the ppm to % questionhoiw many times larger was it???I got 7.8i think its wrong

Reply 836

super121

Original post by Jooost

what was the answer for the ppm to % questionhoiw many times larger was it???I got 7.8i think its wrong

780 000 000 or something along those lines

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Reply 837

King Hotpie

Original post by Davelittle

Well the longest carbon chain was 8, the double bond was between the third and the 4th carbon, there were methyl groups on the 3rd and 7th Carbon.

Therefore 3,7-dimethyloct-3-ene

I believe if you draw out 2,6- dimethyloct-5-ene it's exactly the same- are there any specific naming rules for this, or are they both allowed? How many marks was it, in case they aren't :colone:

Reply 838

Charliestrutt4

Original post by ambbs

Anyone else hate that last 6 mark question on the advance notice? Thought the paper was going alright up until I got to that question, I didn't have a clue!

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I didn't like it either!! I didn't see the N2O equations on the 2nd page.... D:

Reply 839

super121

Original post by King Hotpie

I believe if you draw out 2,6- dimethyloct-5-ene it's exactly the same- are there any specific naming rules for this, or are they both allowed? How many marks was it, in case they aren't :colone: