AQA Chemistry Unit 3 GCSE 24.05.12

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Think theyre all fine, except for the last one, i think you had to stress that the pH was UNDER 7, not just that the weak acid has higher, or you couldve specified e.g. weak is 4-7, strong is 1-4 ,dunno though ull most likely get

Ahh, okay. Thank you :smile:

I hope you did well :smile:

Reply 41

PinkPiglet

I thought this exam was ok easier than I thought! But some of the calculations were complicated:-/

This was posted from The Student Room's iPhone/iPad App

Reply 42

emily_p3

Original post by mt1995

Don't mean to be a downer but surely as they used dilute hydrochloric acid rather than nitric acid, then the precipitate was formed due to the chloride ions in the acid rather than in the egg shell and therefore it can't be proved whether it did contain chloride ions??

it was sating thanks for clearing up the confusion i got it wrong haha

Reply 43

dylan.pv

Original post by mt1995

Yeah this is what i got aswell, as it did say he added silver nitrate solution to the colourless solution that was formed earlier

Reply 44

mt1995

Original post by dylan.pv

Yeah this is what i got aswell, as it did say he added silver nitrate solution to the colourless solution that was formed earlier

Yay

I was starting to think that I had overcomplicated things as all my friends put yes. At least there's one other person who agrees

Reply 45

iBillyB

its probably just me but for the concentration i got 0.63? can someone please tell me how they got 0.61 :smile:

thanks

Reply 46

emily_p3

Original post by iBillyB

its probably just me but for the concentration i got 0.63? can someone please tell me how they got 0.61 :smile:

thanks

it was the volume of the two substances times each other then divided by the number of moles :smile:

Reply 47

iBillyB

Original post by emily_p3

it was the volume of the two substances times each other then divided by the number of moles :smile:

Was one of the volumes 31.75? :s-smilie:

Reply 48

emily_p3

Original post by iBillyB

its probably just me but for the concentration i got 0.63? can someone please tell me how they got 0.61 :smile:

thanks

sorry ignore the first one it was the NaOH volume and the number of moles time each other then divided by the volume of the vinegar

Reply 49

mt1995

Original post by iBillyB

Was one of the volumes 31.75? :s-smilie:

I think it was 31.5

Reply 50

emily_p3

i have forgotten what the amounts were sorry, put the equation i used was
Volume of acid x Concentration of acid = Volume of Alkali x Concentration of Alkali
sorry got the reply wrong again i meant concentration(its been a long day :wink:

)

Reply 51

iBillyB

Original post by emily_p3

sorry ignore the first one it was the NaOH volume and the number of moles time each other then divided by the volume of the vinegar

ahh thanks :smile:

what were the two volumes though? :smile:

Mark scheme?

Original post by iBillyB

ahh thanks :smile:

what were the two volumes though? :smile:

was it 31.5 and 25? conc of NaOH 0.5?

Reply 54

iBillyB

Pardon me if I'm wrong :tongue:

but 0.5/1000 x 31.5 = 0.01575, 0.01575/25 x 1000 = 0.63?

I think anyway :tongue:

Reply 55

maxtate

Original post by iBillyB

Pardon me if I'm wrong :tongue:

but 0.5/1000 x 31.5 = 0.01575, 0.01575/25 x 1000 = 0.63?

I think anyway :tongue:

Its a million percent 0.61, but forgot all values so dunno how i got lol

Reply 56

SaraBB

could someone post an unofficial mark scheme please :smile:

Reply 57

iBillyB

Original post by maxtate

Its a million percent 0.61, but forgot all values so dunno how i got lol

It was a titration calculation and thats the way you do them? these are the values that i remembered and others did, i wouldn't be so certain its 0.61, it might be butttt........ what did you guys get?