You are Here: Home

# Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

• View Poll Results: Which topic(s) are you finding most difficult?
Shapes of molecules and ions
11.66%
Intermediate bonding and bond polarity
15.95%
Intermolecular forces
9.82%
Redox
17.79%
Group 2 & 7
40.49%
Kinetics & Equilibria
14.11%
Organic Chemistry - Alcohols and Halogenoalkanes
39.26%
Mechanisms
26.38%
Green Chemistry
28.83%

What are you doing? The correct procedure is to find the percentage uncertainty in each measurement and then add them up since your combining the measurements. Which is 0.04/10+0.04/10=0.8%.

Clearly you were thinking along the same lines are our examiners. I don't know if they have any clue what they're doing though; I was told I couldn't use the dot multiplier for multiplication and had to use a cross just because they "might not know enough maths", which I think is frankly ridiculous.
Each measurement has uncertainty 0.4%. It follows that the overall uncertainty is 0.4%. Say you have two bags of marbles which you know each contain 5 +/- 1 marbles. The overall absolute uncertainty is 10+/-2 marbles, but the percentage uncertainty remains the same.
2. will melting temp of group 2 come up?
3. (Original post by maryam1996)
Thank you so much , but what about if it's an elemenation reaction is it nucleophilic or electrophilic.
Neither. It's "leaving group" elimination. Not that this will come up.
4. Do we need SN1 vs SN2? Or is SN1 the only one we ever need to know how to draw?

(Original post by Masturchess)

That's what I did, I think. I doubled the % error since you had to use the equipment twice; the 20 I got because you had to add 10cm to 10cm in a mixture, which would mean the total volume of the whole mixture was 20cm^3.
My mistake, sorry! You're absolutely right.

(Original post by metaltron)
Each measurement has uncertainty 0.4%. It follows that the overall uncertainty is 0.4%. Say you have two bags of marbles which you know each contain 5 +/- 1 marbles. The overall absolute uncertainty is 10+/-2 marbles, but the percentage uncertainty remains the same.
*Slaps head* What was I thinking? Add magnitude of uncertainties when adding or subtracting measurements, add percentage uncertainties when multiplying or dividing measurements.
5. (Original post by Priya08)
thank you..okay I understand it now..one last question so is there such thing as permanent instantaneous dipole?
Permanent dipoles only form between polar molecules : the delta negative and delta positive have electrostatic attraction.
6. Is this exam in the afternoon?

Posted from TSR Mobile
7. (Original post by James A)
Is this exam in the afternoon?

Posted from TSR Mobile
Yes
Do we need SN1 vs SN2? Or is SN1 the only one we ever need to know how to draw?
I think it's came up before to draw the intermediate for a primary and a tertiary halogenoalkane or something similar so i think we need to know them. Sn1 has the cation and Sn2 has the 2 partial/temporary bonds to the halide and nucleophile
9. Do we meed to know the catalysts? If anyone knows help is appreciated cheers as in the irdium iodide etc

Posted from TSR Mobile
10. As a general note, double check your answers to multiple choice questions when you ask them, twice it has happen that the original asker gave the wrong 'answer'. It's just going to confuse others, who will confuse you even more...

Posted from the TSR iPad app
11. (Original post by ASStudent)
Do we meed to know the catalysts? If anyone knows help is appreciated cheers as in the irdium iodide etc

Posted from TSR Mobile
nope i guess they might just ask it's function how it would it work.
they wold probably give it in question.
remember Cl radical and NO are catalyst too.
12. (Original post by geor)
We have to know phosphorus?!
I'm going to memorize it tomorrow morning just in-case, but what do you think ? There's way too much to remember I think I'll be getting section B & C out of the way first thing !
13. (Original post by marz1994)
will melting temp of group 2 come up?
may be to compare Carbonates or Nitrate regarding thermal stability, just to give u an idea wich has more melting temp. mostly they'll gv in the paper.
14. Hi, can someone please explain to me why the c-Br bond is more electronegative than the C-I bond. I also don't understand why thermal stability of metal carbonates increases down group 2 even-though that as the cation ion gets larger down the group doesn't that make it less stable as it can easily lose electrons now as it has more sheilding and is further away from the nucleus as it has a reduced polarising power. I'm quite confused,
Thank you
15. (Original post by geor)
We have to know phosphorus?!
It's just P4 + 6X2 -> 4PX3, P4 + 10X2 -> 4PX5. I can't see anything involving O coming up but just bear in mind that POX3 is not uncommon.

Didn't you get Gold in the U6 Olympiad? This shouldn't be hard
16. Why are HCFCs less stable that CFCs?
17. (Original post by posthumus)
I'm going to memorize it tomorrow morning just in-case, but what do you think ? There's way too much to remember I think I'll be getting section B & C out of the way first thing !
Every phosphorous reaction that can come up, can be worked out on the spot. As far as I know, POX3 comes from P4 + 6X2 + 2O2 -> 4POX3.
18. (Original post by geor)
Shush nowww But thanks.
Are you doing this exam?
Yah.
I wish now that I had revised more for the exam itself. I'll be applying for Chemistry but with better scores in Physics and Maths at this rate
19. http://www.edexcel.com/migrationdocu...e_20110120.pdf Q's 7c, 11d, 6b
20. (Original post by geor)
Haha - brilliant! Yeah I was aiming for the full UMS but the grade boundaries are just so ridiculous, have to be so precise.
I'm planning to apply for chemistry too! Where are you looking at?
Depending on my scores (in Chemistry, Physics & Maths) either Cambridge or Oxford, as well as Durham (NatSci), Imperial (Chemistry) and Nottingham (NatSci). Not sure where else atm. What about you?

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 29, 2014
Today on TSR

### Does race play a role in Oxbridge admissions?

Or does it play no part?

### The worst opinion about food you'll ever hear

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

Can you help? Study Help unanswered threadsStudy help rules and posting guidelines

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.