OCR Chemistry A 2016 unofficial mark scheme 27/05/16

I put H2O, didn't even think of a hydroxide! Wow.

You cannot use Br2 because you will make a dihaloalkane and you cannot make an alcohol from dihaloalkane. You had to use HBr to make haloalkane and then NaOH to make alcohol.

The end product was a diol...

You cannot use Br2 because you will make a dihaloalkane and you cannot make an alcohol from dihaloalkane. You had to use HBr to make haloalkane and then NaOH to make alcohol.

No, you had to put the x 10^22, and also I don't think significant figures was specified in the question

24.8 for h2s04 and 0.912 for the kc value

Here's my attempt at an unofficial mark scheme, it is for the OCR Chemistry A, new spec, breadth in chemistry paper, really can only put the maths questions down, but if there are written ones I can remember I will put them down. This is only really for comparison of numbers, and general ideas

Multiple choice:
BCDACBBDCBCBBCBDDBBD (if anyone happened to store their multiple choice answers on there calculator, please post them below to compare)

The end product was a diol...

There's probably more than one correct method

What was the question?

Same number of protons and electrons, different number of neutrons

I didn't put "electrons" will I lose marks?

Relative atomic mass: 63.62
No of atoms in 5.00g coin: 3.98 x 10^22 (3sf)

do you remember the calculation for the coin question?

Percentage error of water removed mass: 1.72%

Ways to reduce percentage uncertainty: use a larger mass of crystals to get larger mass of water removed, reducing % error

how to make sure all the water's gone: I put reweigh and reheat repeatedly until constant mass is achieved.

Volume of H2SO4 required to neutralise NaOH: 24.3cm^3
Enthalpy change of reaction: -58.5 kJmol^-1
Concentration of KI required: 3.3 moldm^-3
Concentration in equilibrium question: 0.876 moldm^-3

Homologous series: alkenes
General formula: CnH2n

there was a question after this bit I don't remember, all I know is I put: h2, nickel catalyst.
then there was a diagram: BLANK - H2S04 catalyst and heat - THE GIVEN ALKENE (I can draw it out from memory but idk how to put it on here) - ANOTHER BLANK

Electron configuration of bromide ion: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6

Equilibrium question: The equilibrium position will shift to the right, as the forward reaction is exothermic, in an attempt to reduce the effect of the temperature decrease. The equilibrium position will also shift to the right as there are fewer gas molecules in the products of the forward reaction, in an attempt to reduce the effect of the pressure increase. This may vary to the actual conditions as low temperature reduces rate of reaction, and it's expensive to have a high pressure.

what happens when you put chlorine gas into bromine ions:I put chlorine is more reactive that bromine, so it displaces bromine that causes whatever change the question was asking for. ionic equation for the equation given with PBII put: PB^2+ (aq) + 2I- (aq) —> PbI2 (s)

Halogen precipitate colours: chloride, white; bromide, cream; iodide, yellow

Last question: step 1 reagent, Br2, step 2 reagent, NaOH

If anyone remembers the written answers, please post and I'll add them,
Any incorrect (although I don't think there are) please tell and I'll correct

Also, post about how you found the exam, as this will give a good idication of grade boundaries

I also remember a random gas question I got 32.7cm^3

it wasnt a haloalkane thoughit was just an alkane with OH groups on either end

*No of atoms in 5.00g coin: 3.98 x 10^22 (3sf) *

For this one, I got 3.97 x 10^22 for using the RAM calculated in the part before?? Did you have to use the periodic table one or the calculated one?

didn't it ask for the similarities and differences between isotopes of the same element???

The end product was a diol...

Yeah I want an answer to that too. I used the Relative Atomic Mass from the question before because the questions were c) i) and ii) so I presumed they were connected, can't remember what I got though but it was 3. something x10-22

*No of atoms in 5.00g coin: 3.98 x 10^22 (3sf) *

For this one, I got 3.97 x 10^22 for using the RAM calculated in the part before?? Did you have to use the periodic table one or the calculated one?

the kc question may be wrong too as (0.876^2)/2^2+1.2 =1.47 which is not correct as kc was 1.6

Easy is paper, could have been far worse, this was an above average paper so I'm thinking paper two will be an absolute terror, but that should drop the grade boundaries at least...

You multiply 2^2 and 1.2, not add them