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GCSE OCR 21st Century B7 C7 P7 - W/C - Monday 20th June 2016

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yh same it was amazing! for calculating atom economy did you get 4/36*100 = 11.1111%
Original post by MezmorisedPotato
Wonderful paper, apart from a few stupid mistakes (in a six marker but only a few marks), everything else was shockingly pleasant! :smile:


we should make an unofficial markscheme
Original post by 11207ymir
we should make an unofficial markscheme


for energy calculations did people get 587-1134= -547
I thought it went terribly, there was hardly anything on organic chemistry and equilibrium (my favourite) :frown:
It felt like it was mostly chromatography
(edited 7 years ago)
Original post by 11207ymir
yh same it was amazing! for calculating atom economy did you get 4/36*100 = 11.1111%


Yup I got that!
i didn't do much on chromatography as it came up last year, but i thought the paper was alright not amazing, not awful!!
Original post by 11207ymir
for energy calculations did people get 587-1134= -547


Oh no I think I got 547 - 1134 = -587 :s-smilie:
Original post by 11207ymir
yh same it was amazing! for calculating atom economy did you get 4/36*100 = 11.1111%


Yeah I got that one
For the last 6 marker (about the acids) how many marks would I get for being right about the pHs but completely wrong about concentrations? Hopefully I won't be limited to L1 lmao
Was definitely 20% you spenghoulis
Original post by NiamhM1801
For the last 6 marker (about the acids) how many marks would I get for being right about the pHs but completely wrong about concentrations? Hopefully I won't be limited to L1 lmao


probably about 2/3
for that question i talked about the strong acids having the low ph and high concentration if the volume of sodium hydroxide was low as less is needed to neutralise the acid which makes it more concentrated, i think it was acid f that was most strongest and had the highest concentration
Original post by 11207ymir
probably about 2/3
for that question i talked about the strong acids having the low ph and high concentration if the volume of sodium hydroxide was low as less is needed to neutralise the acid which makes it more concentrated, i think it was acid f that was most strongest and had the highest concentration

Surely a low amount of sodium hydroxide would mean a lower concentration as you need less alkali overall?
Original post by reu_taylor
Was definitely 20% you spenghoulis


no it wasnt there were 4 hydrogens in the product and the total mass of reactants was 36 atom economy= mass of hydrogens in products/total mass of all reactants*100
Original post by 11207ymir
probably about 2/3
for that question i talked about the strong acids having the low ph and high concentration if the volume of sodium hydroxide was low as less is needed to neutralise the acid which makes it more concentrated, i think it was acid f that was most strongest and had the highest concentration


Ok that's not too bad then to say I had no idea about concentration
I just assumed that the higher the number in the second column, the higher the concentration of the acid as more alkali is needed to neutralise it, however my friend said that I read that column wrong as she thought it said amount of acid needed to neutralise the alkali whereas I thought it was amount of alkali needed to neutralise the acid. Hey ho
Original post by 11207ymir
no it wasnt there were 4 hydrogens in the product and the total mass of reactants was 36 atom economy= mass of hydrogens in products/total mass of all reactants*100


Exactly, it was 4/20 NOT 36 therefore it was 20%
Original post by reu_taylor
Exactly, it was 4/20 NOT 36 therefore it was 20%

well no one else got it
anyway you will prob get 1mark
Original post by reu_taylor
Exactly, it was 4/20 NOT 36 therefore it was 20%

Wrong, i did the same thing but what i forgot to realise is that there are 2 oxygens so (2x16) + 4 = 36
Original post by Mr_Elmo
Wrong, i did the same thing but what i forgot to realise is that there are 2 oxygens so (2x16) + 4 = 36


Was there actually? I checked it and I don't think there was
Original post by reu_taylor
Was there actually? I checked it and I don't think there was

There was a 2 at the front of the reaction i think so yeah
Original post by Mr_Elmo
There was a 2 at the front of the reaction i think so yeah


Fair enough if it was, but why would the atom economy go down if it was supposedly a "new" method?

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