OCR A-level Chemistry A Paper 1 - 10th June 2025 [Exam Chat]

Reply 1060

xitz_jessix

12

Original post by 4020LeKo18

Oh yeah that makes sense, wishing you luck 🙏💀

I’ll need it 😭 what’s your third subject?

Reply 1061

mith#17

7

Did we need to put the units for Gibbs free energy to get the mark

Reply 1062

xitz_jessix

12

Original post by mith#17

Did we need to put the units for Gibbs free energy to get the mark

Usually they’re in brackets in the MS so dw!

Reply 1063

Masrooler

4

Original post by 4020LeKo18

Yeah my teacher (who is an examiner for OCR) defo said it is cis/trans because the complex ion was square planar

Weren't the 4 ligands connected making it only 2 groups and they can't show cis trans so it was an optical isomer?

Reply 1064

yam11

3

Original post by Masrooler

Weren't the 4 ligands connected making it only 2 groups and they can't show cis trans so it was an optical isomer?

No they weren't optical isomers. You can't have optical isomerism in square planar complexes. If you did the mirror image, you would see that the mirror image is actually superimposable with the original as you could just rotate it and it would be exactly the same. Since it is not non-superimposable, it can't be optical isomerism. It is cis trans, the compound drawn was the trans isomer, you just had to draw the cis isomer.

(edited 3 weeks ago)

Reply 1065

sehajss

10

Original post by yam11

No they weren't optical isomers. You can't have optical isomerism in square planar complexes. If you did the mirror image, you would see that the mirror image is actually superimposable with the original as you could just rotate it and it would be exactly the same. Since it is not non-superimposable, it can't be optical isomerism. It is cis trans, the compound drawn was the trans isomer, you just had to draw the cis isomer.

its not square planar

Reply 1066

Unrei

10

Original post by xitz_jessix

Usually they’re in brackets in the MS so dw!

Honestly I wouldn't be too sure I did a past paper where we had to have the units, took me by surprise but yh they could specify to have units too

Reply 1067

Unrei

10

Original post by yam11

No they weren't optical isomers. You can't have optical isomerism in square planar complexes. If you did the mirror image, you would see that the mirror image is actually superimposable with the original as you could just rotate it and it would be exactly the same. Since it is not non-superimposable, it can't be optical isomerism. It is cis trans, the compound drawn was the trans isomer, you just had to draw the cis isomer.

Someone just ask their chemistry teacher, we have been debating this for too long now

Reply 1068

4020LeKo18

9

Original post by Unrei

Someone just ask their chemistry teacher, we have been debating this for too long now

I did and he said cis/trans and he’s an OCR examiner, it’s settled 😭😭

Reply 1069

yam11

3

Original post by sehajss

its not square planar

It is square planar. If the example was shown from the front side, there would be two bonds that were wedges and two bonds that were hashes (like in the examples in textbooks). In the question, the example was shown from a top side view which would show all the bonds in the same plane (since it is square planar) and therefore the bonds as normal lines. I think it was done on purpose to confuse students.

Reply 1070

Masrooler

4

It's only 2 marks anyway guys just get the other 98 and you're fine

Reply 1071

sehajss

10

Original post by Masrooler

It's only 2 marks anyway guys just get the other 98 and you're fine

should be talking about p2 rn 😭

Reply 1072

Bbibbisvt

1

Someone pls send me the link to the unofficial markscheme!!!

Reply 1073

Shri808

2

was there a Kc/Kp on this paper i dont remember

Reply 1074

Unrei

10

Original post by Shri808

was there a Kc/Kp on this paper i dont remember

Kp yes

Reply 1075

Skye123eliz

3

Was there a mcq on born harber cycles? And if so what was it?

Reply 1076

Moazan1

5

Original post by Skye123eliz

Was there a mcq on born harber cycles? And if so what was it?

Why 2nd electron affinity is endothermic bc of electron repulsion

Reply 1077

Amna_tutor

7

Original post by incidental-ruse

Guys if I messed up the units for the rate 5 marker and put dm6mol-2 instead of dm6mol-2s-1 am I capped at a certain amount of marks or is it only one mark lost for the mistake

You'll lose 1 mark even if it was a 6 marker

Reply 1078

Amna_tutor

7

Original post by crystalemonz

I put bond angle 107.5 for PH3 not 107😔 hopefully the examiner rounds the number down for me 😜

Usually they accept a generous range of angles - yours is very close, so I wouldn't worry :smile:

Reply 1079

Amna_tutor

7

Original post by yaaaziiiii

I did all the right working out but multiplied by the wrong mr. Do you think i’d only lose one mark max😭 I got 1.56g but if i multiplied by the right mr i would’ve gotten 2.02g

You will lose 1 mark. Even if you made a mistake in the very beginning of the question, they would recalculate all the steps with your wrong value, so you'd lose 1 mark and get the rest as ECF.

OCR A-level Chemistry A Paper 1 - 10th June 2025 [Exam Chat]

Unofficial Mark Scheme

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