The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

Scroll to see replies

Original post by h3rmit
If you get a U, probably not. Some teachers will allow those getting E's to pass through on a case by case basis. Revising is a better use of your time that worrying about your grades though


give me some key topics to revise please i feel like im going to fail
Original post by ineedhelpppl
give me some key topics to revise please i feel like im going to fail


This is kind of what the practice papers you did in class (and the past and specimen papers you've been doing yourself) are for

I'd recommend looking through the OCR specification and if anything there doesn't ring a bell, you need to revise it
If a 1 mark question was why does OH- ions act as a nucleophile? Is it because it's an electron pair donor


Posted from TSR Mobile
For one mark, that would be a good answer.

Posted from TSR Mobile
Reply 144
Avatar for oni176
oni176
7
Original post by Fish40
If a 1 mark question was why does OH- ions act as a nucleophile? Is it because it's an electron pair donor
.
Posted from TSR Mobile


Yes, correct.
Is there a mechanism we need to know for radical substitution? I know about initiation, propagation and termination but is there any curly arrows or anything we need to know??
Reply 146
Avatar for oni176
oni176
7
Original post by Clintbarton
Anyone got any predictions?


Posted from TSR Mobile


Definitely there will be questions on the different mechanisms; nucleophilic substitution, electrophilic addition and free-radical substitution needs to be known.

Possible six markers can be based on a combination of different topics. It is difficult to predict 6 markers for chemistry. The practice paper had 6 markers on alcohols and dyanmic equilibrium which are good topics to be asked on. However, the practice paper may not look similar to actual papers...
Reply 147
Avatar for oni176
oni176
7
Original post by mollyayo
Is there a mechanism we need to know for radical substitution? I know about initiation, propagation and termination but is there any curly arrows or anything we need to know??


Free radical substitution does not form curly arrows, they form radicals only.

Electrophilic addition and nucleophilic substitution are the only mechanisms that involve curly arrows and any relevant dipoles.
Reply 148
Avatar for oni176
oni176
7
Original post by ineedhelpppl
give me some key topics to revise please i feel like im going to fail


Different mechanisms:
Free radical substitution
Nucleophilic subsitution
Electrophilic addition

Dynamic equilibrium and working out the constant K
Be confident applying calorimetry calculations
Be condident working with mole questions, percentage yield, atom economy

Alcohols, combustion general structure boiling points etc.
Writing equations for alcohols (partial combustion ---> aldehyde, complete combustion ---> carboxylic acid)

Tests for halide ions, carbonate ions, sulfate ions, ammonium ions
Basic information about covalent bonding, ionic bonding and metalic bonding in terms of electrical conductivity, boiling points etc

Ensuring that you know information about ozone depletion and writing the radicals for chlorofluorocarbon

Boiling points, formation of bonds in alkanes and alkenes. Their basic structure, information etc.

Mass spectrum

Group 7 halogens (trends down a group, the bond that occurs between them, knowing the benefits and risks of chorine, knowing disproportional reaction)

Uses for group 2 elements, trend down a group

Ionisation energies.
Original post by oni176
Free radical substitution does not form curly arrows, they form radicals only.

Electrophilic addition and nucleophilic substitution are the only mechanisms that involve curly arrows and any relevant dipoles.

Hahah Thankyou... Shows how much I know for my exam.
So do you get asked to do the mechanism for free radical substitution?? You don't do you, just the equations?


Posted from TSR Mobile
We should keep asking questions back and forth on this thread.


Posted from TSR Mobile
Original post by Fish40
So do you get asked to do the mechanism for free radical substitution?? You don't do you, just the equations?


Posted from TSR Mobile


The equations are a mechanism
Yo please can I have some help with this question.
Curing an experiment 11.50g of ethanol is completely burnt in air. During the combustion 341.5KJ of heat energy is released.
What is the enthalpy change of combustion of ethanol?

A) -341.5kjmol-1. B) -1366KJmol-1. C) -85.38KJmol-1. D) -34.15KJmol-1

Cheers 😊
Original post by harryleavey
The equations are a mechanism


Do you ever have to draw the mechanism for free radical substituion? Or do you just get asked to write the equations?


Posted from TSR Mobile
Original post by Farmerjj
Yo please can I have some help with this question.
Curing an experiment 11.50g of ethanol is completely burnt in air. During the combustion 341.5KJ of heat energy is released.
What is the enthalpy change of combustion of ethanol?

A) -341.5kjmol-1. B) -1366KJmol-1. C) -85.38KJmol-1. D) -34.15KJmol-1

Cheers 😊


ImageUploadedByStudent Room1464249732.328589.jpg


Posted from TSR Mobile
Original post by Fish40
Do you ever have to draw the mechanism for free radical substituion? Or do you just get asked to write the equations?


Posted from TSR Mobile


As I just said, the equations are a mechanism.
If you are under the impression that there is a 'displayed mechanism' for free radical substitution reactions - there isn't one.

I have attached a picture of the 3 mechanisms we need to know.
I hope this helps :smile:

Picture Credit: Revision Cards for OCR A Chemistry, RevisionTools.co.uk

Screen Shot 2016-05-26 at 09.13.48.png92.2KB
Original post by harryleavey
As I just said, the equations are a mechanism.
If you are under the impression that there is a 'displayed mechanism' for free radical substitution reactions - there isn't one.

I have attached a picture of the 3 mechanisms we need to know.
I hope this helps :smile:

Picture Credit: Revision Cards for OCR A Chemistry, RevisionTools.co.uk



Thank you


Posted from TSR Mobile
Any questions your struggling with, post here


Posted from TSR Mobile
Original post by Fish40
We should keep asking questions back and forth on this thread.


Posted from TSR Mobile


Good idea.

The boiling points of three liquids, A, B and C are 65, 141, and 80 respectively. Liquid A reacts with liquid B to produce liquid C and water. Distillation of the reaction mixture produces four pure liquids, which are collected as they form in separate beakers. Which beaker (1st, 2nd, 3rd or 4th) would contain water?


Posted from TSR Mobile

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you