Chemistry: Post your doubts here!

[techgeek]

Solve OCR papers then

yep seems like that

 

[Rizwan Javed]

yep seems like that

Different variants have same kind of questions?
I solved all variant 11s now I came back to 12 ones and they all basically seem the same

Only two papers in every Oct/Nov session only are same. Otherwise, every other paper is different.

 

[ahmedish]

June 13 P41, 1) c) ii)
mark scheme ays its forward (more product) because E is more than 0 (its positive)
but isnt that always the case ?? Even if both half cells is negative its going to be (-0.12)-(-0.67)= positive??
so why are there more products?

 

[farhan141]

Any advice on how to study whole chemistry in 2 weeks? I have done Maths and Physics with past papers just left with chem. Any advice or links/pdfs/pics/notes would be really helpful.

 

[The Sarcastic Retard]

June 13 P41, 1) c) ii)
mark scheme ays its forward (more product) because E is more than 0 (its positive)
but isnt that always the case ?? Even if both half cells is negative its going to be (-0.12)-(-0.67)= positive??
so why are there more products?

If E cell is positive then the reaction will be proceeding in forward direction. This means more products will be formed.

 

[The Sarcastic Retard]

Any advice on how to study whole chemistry in 2 weeks? I have done Maths and Physics with past papers just left with chem. Any advice or links/pdfs/pics/notes would be really helpful.

It depends! chemguide is one of the best site for chemistry. ^_^
Goodluck.

 

[techgeek]

Only two papers in every Oct/Nov session only are same. Otherwise, every other paper is different.

what do you mean by only two papers are same?

 

[Rizwan Javed]

what do you mean by only two papers are same?

There are 3 variants of Chemistry papers. Out of those 3, 2 are same in every Oct/Nov session.

 

[techgeek]

There are 3 variants of Chemistry papers. Out of those 3, 2 are same in every Oct/Nov session.

oh really? I didn't know that, thanx
yaeh, therefore yesterday's paper was the same I had solved already but today's turned out to be different

 

[fatimarehman]

Can someone help me with chemistry paper 5 Oct Nov 2014 var 52 Q1 part d subpart I and ii. How to compare the concentrations or molecules?

 

[ahmedish]

If E cell is positive then the reaction will be proceeding in forward direction. This means more products will be formed.

E cell is always positive though

 

[fatimarehman]

Can someone explain me chemistry paper 5 Oct Nov 2014 var 52 part d sub part I and ii.

 

[qwertypoiu]

Help part b ivView attachment 60404

J is formed by replacing H from the tertiary carbon in the middle. This happens at rate=21.
K is formed by replacing H from any one of the primary carbons on the side. It happens at rate =1, but since there are 9 such H atoms, 9*1=9
So relative amounts will be 21:9

 

[The Sarcastic Retard]

E cell is always positive though

Not always...

 

[ahmedish]

Not always...

I realised.
Can you explain why having a positive E cell mean there are more products?

 

[ahmedish]

Not always...

wait i dont get how E cell can be negative LOL
How can E cell be negative?

 

[TariqBhai]

June 13 P41, 1) c) ii)
mark scheme ays its forward (more product) because E is more than 0 (its positive)
but isnt that always the case ?? Even if both half cells is negative its going to be (-0.12)-(-0.67)= positive??
so why are there more products?

wait i dont get how E cell can be negative LOL
How can E cell be negative?

I realised.
Can you explain why having a positive E cell mean there are more products?

Ecell will be positive for reactions which are feasible/spontaneous in the forward direction. If Ecell is negative then the reaction is feasible only for the backward direction.

Since you calculated that Ecell was positive then the reaction:
2Fe + 2I <=> 2Fe+ I 2
Will only occur in the forward direction: 2Fe + 2I => 2Fe+ I 2

If Ecell was negative then the reaction would only occur in backward direction: 2Fe+ I 2 => 2Fe + 2I

MS is talking about Ecell and not E.

 

[The Sarcastic Retard]

I realised.
Can you explain why having a positive E cell mean there are more products?

wait i dont get how E cell can be negative LOL
How can E cell be negative?

Ecell will be positive for reactions which are feasible/spontaneous in the forward direction. If Ecell is negative then the reaction is feasible only for the backward direction.

Since you calculated that Ecell was positive then the reaction:
2Fe + 2I <=> 2Fe+ I 2
Will only occur in the forward direction: 2Fe + 2I => 2Fe+ I 2

If Ecell was negative then the reaction would only occur in backward direction: 2Fe+ I 2 => 2Fe + 2I

MS is talking about Ecell and not E.

As TariqBhai explained, if Ecell value is positive means reaction will be occurring. As reaction is occurring that simply means reaction is moving in forward direction. This means more product. And the reaction which arent feasible are the ones that have negative Ecell and the reaction will move backwards.

 

[MafaldaC]

octo nov 2015 mark scheme 21??????

 

[The Sarcastic Retard]

octo nov 2015 mark scheme 21??????

I couldnt find any ms. But here is what u can get idea similar to ms. http://papers.gceguide.com/A Levels/Chemistry (9701)/9701_w15_er.pdf
scrol down till u get paper 21 er.