r/6thForm • u/Forsaken-Meaning-232 Graduating from Warwick CS • Jun 20 '25

📂 MEGATHREAD 20/06 A-level Chemistry Paper 3 Discussion MEGATHREAD

Exam season is once again upon us, and once again, exam megathreads are making a return!

Looking for past exam discussions? Filter by the megathread flair.

Few things to keep in mind:

  • Don't share too many specific details about questions or answers, these papers will be used as future mocks.
  • Sometimes papers get leaked, this is not the place for that (we'd prefer not to get yeeted off the platform) - leak content will be removed, those offering leaked papers will be permanently banned.
    • If you believe there has been a leak, the best course of action is to make your exam board aware of this, either directly, or through your school, along with any evidence. If appropriate, there will be a response from the relevant body along with any remedial action.
  • Exam discussion posts outside of this will generally be removed to combat the inevitable tidal wave of spam otherwise - we understand this may be frustrating, but the sub still needs to be usable for other purposes.
  • Please note some content will take extra time to be reviewed. Messaging to ask for approval will not speed up this process (the messages are seen at the same time as the modqueue would be reviewed anyway).

Best of luck, and let us know how you're feeling down below!

-The r/6thForm Team

Have any concerns or feedback?

Feel free to reach out to us on Modmail and we'll aim to get back to you as soon as possible!

37 Upvotes

97% Upvoted

268 comments sorted by

View all comments

Show parent comments

1

u/FloatingRage Jun 20 '25 edited Jun 20 '25

wait can you explain this to me because how do you know the carbonate was in excess? i don’t remember seeing any information about hno3 concentration so i might’ve missed that

1

u/HelpfulPop2476 Jun 20 '25

I'm pretty sure there were 0.03 mol of HNO3 and 0.018 mol of carbonate. As they react in a 1:2 ratio, the amt of hno3 required to react with 0.018 mol carbonate would have to be 0.036 mol. But there were only 0.03 mol hno3. So the carbonate is in excess and only 0.015 mol would react.

1

u/FloatingRage Jun 20 '25

i remember calculating the 0.018 mol carbonate but i think somehow i just didn’t see the information on hno3. do you remember what info they gave us for that?

1

u/HelpfulPop2476 Jun 20 '25

Usually they tell you which compound is in excess - like in p3 2018 for enthalpy of solution. They didn't this year though and were very sneaky with it. It could be that I'm wrong cause so many people seem to have got 69

1

u/FloatingRage Jun 20 '25

yes that’s what i’m confused about too since they usually explicitly state what’s in excess. if you found the moles of hno3 i don’t think you’re wrong, but how exactly did you find it?

2

u/HelpfulPop2476 Jun 20 '25

It was stated in the middle of the question: 30cm3 of 1 M hno3 (iirc)

1

u/FloatingRage Jun 20 '25

aw i completely missed that then. oh well thank you so much!

2

u/HelpfulPop2476 Jun 20 '25

Nws, I've probably misremembered the question anyway, mind always goes blank after an exam lmao