AQA A Level Chemistry Paper 3 20th June 2018 Unofficial Markscheme

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Reply 20

tan_pz

Ethylamine>ammonia>phenylamine?

Reply 21

HeartBlink

Original post by BMW520D

I got -65 something or something in the -60's.5 kjmol... because you had to divide moles by what was not in excess

So divide Q by 0.02mol or something.

It was per mole of water, so 1:2 ratio id you got the equation right.

And also, did we have to put an arrow or an eqm sign in the equation? I put an eqm sign since it was a weak acid, which i realised when they said why - 33 is less than - 57 with H2SO4

Reply 22

Sweetie08

what rate did you get when [H+] is 0.35? did you just have to find the gradient of the tangent at 0.35 because in the question it said only concentration of I- affected rate?

Reply 23

brendonurine

Original post by Lalalozzaland

How did everyone put to find initial rate in the 6 marker!? I put 1/time

Same, did you say stop stop watch when blue starts to appear or when turns dark blue?

Reply 24

london256145

guys please help i don't know why but on the last question i got like -2.6x10³and i don't know why ?? :bawling:

Reply 25

Sweetie08

Original post by tan_pz

Ethylamine>ammonia>phenylamine?

yes i wrote that as its links to of strength of base

Yield : 75.9

Original post by brendonurine

Same, did you say stop stop watch when blue starts to appear or when turns dark blue?

I think I just put when it turns blue because I don’t think it’s a gradual change, it goes straight to dark blue

Reply 28

Daniortall

Enthalpy of Neutralisation?

-52.25 or -105.5 ?

Reply 29

Sweetie08

Original post by london256145

guys please help i don't know why but on the last question i got like -2.6x10³and i don't know why ?? :bawling:

calorimetry q?

Reply 30

Jadejay

Original post by eliza154

k = 1.2x10^-3
rate = 4.4x10^-4
temperature change = 2.1
uncertainty = 9.52%
calorimetry = 33.6 kJ/mol

I thought it asked for the temperature at minute 4 not the temperature change
For rate I got 4.2x10^-4 but it was probably because our graphs were different and I think the calorimetry one needs a negative sign