Chemistry P41 How was it?

[vivo990]

It was more towards the products side

If you look at the dissociation of ethanoic acid, for example, the reaction is feasible (and actually it does occur), BUT, the equilibrium still lies more to the left.​

The Ecell, value was 0.23V, which is very low, so the reaction is not that spontaneous .​

So it actually lies more to the reactants.

 

[Starry_night]

If you look at the dissociation of ethanoic acid, for example, the reaction is feasible (and actually it does occur), BUT, the equilibrium still lies more to the left.​

The Ecell, value was 0.23V, which is very low, so the reaction is not that spontaneous .​

So it actually lies more to the reactants.

Here, I found this: http://chemwiki.ucdavis.edu/Analyti...namics#E.c2.b0cell.3a_Standard_Cell_Potential

If u go to section 7 (the summary table), the first row says that if Ecell is greater than 0 (it was +0.23 in the exam I think), it means that reaction proceeds in the forward direction favouring the products. It also adds that the reaction is spontaneous.

 

[vivo990]

OK, this is the case if the reaction goes to completion, but in our case its not.
The positive value shows that the reaction can proceed forwardly. The magnitude of that value indicate, how spontaneous then reaction is.

 

[iKhaled]

is the value of Kc 25 or not ???

 

[Starry_night]

OK, this is the case if the reaction goes to completion, but in our case its not.
The positive value shows that the reaction can proceed forwardly. The magnitude of that value indicate, how spontaneous then reaction is.

I don't think it's for reactions that go to completion because the whole page talks about equilibrium reactions (and if the reaction did go to completion, there wouldn't be a case for it to proceed backwards in the same conditions).
Just above the table, it says this: *If the E° value of the reaction is negative, then the reaction is NOT spontaneous and therefore the reverse reaction is occuring and the electrons are flowing in the opposite direction.
This is the opposite of our case. Our case is that Ecell is positive, so the forward reaction is occuring more than the backward.

But anyway, I guess only the mark scheme can say for sure..!

 

[marz_katy]

what was the three different chromatography used??

 

[vivo990]

I

I don't think it's for reactions that go to completion because the whole page talks about equilibrium reactions (and if the reaction did go to completion, there wouldn't be a case for it to proceed backwards in the same conditions).
Just above the table, it says this: *If the E° value of the reaction is negative, then the reaction is NOT spontaneous and therefore the reverse reaction is occuring and the electrons are flowing in the opposite direction.
This is the opposite of our case. Our case is that Ecell is positive, so the forward reaction is occuring more than the backward.

But anyway, I guess only the mark scheme can say for sure..!

If the Cell is not positive, the Forward reaction is NOT FEASIBLE in the first place.

 

[Thampi4]

I have very strong feeling that this is the right answer. I believe strongly that what you have got, although many did not get it, is right. There is no way of comparing the iron 3 and iron 2, it is EQUILIBRIUM.
Meaning you have to compare reactants with reactants, and products with products.

Oh ok
I c what u mean
I get how u got it

 

[iKhaled]

Oh ok
I c what u mean
I get how u got it

is Kc 25 wrong ?

 

[Thampi4]

What was the value of rate constant
I got 1.6x10^ - something

 

[Thampi4]

Yea

 

[iKhaled]

why is it wrong ? how can we arrive to the correct answer then ?

 

[Starry_night]

what was the three different chromatography used??

I put thin-layer, paper, gas-liquid (in that order).

 

[Thampi4]

See page 2 of this thread

 

[marz_katy]

I put thin-layer, paper, gas-liquid (in that order).

even i rote the same=D r u sure about ur ans??

 

[Starry_night]

even i rote the same=D r u sure about ur ans??

I'm pretty sure because the testing for drugs in athletes' urine comes in the Coursebook under gas-liquid, the dyes in foodstuffs is comparable to the dyes in ink (which are usually separated by paper chromatography) and the insecticides dissolved in water I thought was thin-layer because u need a polar solute and if the insecticides were dissolved in water it must mean that they are polar (also because it was the only one left to choose from, excluding HPLC).

 

[marz_katy]

I'm pretty sure because the testing for drugs in athletes' urine comes in the Coursebook under gas-liquid, the dyes in foodstuffs is comparable to the dyes in ink (which are usually separated by paper chromatography) and the insecticides dissolved in water I thought was thin-layer because u need a polar solute and if the insecticides were dissolved in water it must mean that they are polar (also because it was the only one left to choose from, excluding HPLC).

yaayyyy=D you had so much in ur head wile answering=P i just wrote what my heart said XD tnx anyway!!

 

[marz_katy]

yaayyyy=D you had so much in ur head wile answering=P i just wrote what my heart said XD tnx anyway!!

and what was the correct ans u chose for the dna fingerprinting?

 

[1357913579]

I'm pretty sure because the testing for drugs in athletes' urine comes in the Coursebook under gas-liquid, the dyes in foodstuffs is comparable to the dyes in ink (which are usually separated by paper chromatography) and the insecticides dissolved in water I thought was thin-layer because u need a polar solute and if the insecticides were dissolved in water it must mean that they are polar (also because it was the only one left to choose from, excluding HPLC).

same bro

 

[1357913579]

and what was the correct ans u chose for the dna fingerprinting?

the hair and the leather.