Chemistry P41 How was it?

[Thampi4]

Y

Ok good. What about the next part of the question, where there were like 4 reagents and they said observations. Was it in each column one was no reaction and the other gives a product?

yea
It was the phenol with the side chain doesn't oxidize

 

[Marks&Spencers]

U got 24 too
It was to the right cuz Ecell was positive

Ok can you please explain to me how you got that 25? You seem like a smart person and I didn't get that answer so now I'm kind of freaking out. I got 2.5 x 10^9. I know it's a big number but I checked it a million times and this is how I got it. I did it the same way another poster on this thread did it.

 

[queen of the legend]

It was more towards the products side

but it was EQUILIBRIUM ...plus there was no change in temp, pressure or concen. of any reactants and no catatlyst to increase the rate ....i dont knw but i wrote conc. remains equal on both sides of the equation
the reduction potential just tels us if the reaction (forward) is feasible or not

 

[queen of the legend]

Ok can you please explain to me how you got that 25? You seem like a smart person and I didn't get that answer so now I'm kind of freaking out. I got 2.5 x 10^9. I know it's a big number but I checked it a million times and this is how I got it. I did it the same way another poster on this thread did it.

dnt freak out ...we dnt knw yet which answer is correct ....if anyway u got it wrong ..i am sure u'll get awarded for the method

 

[Marks&Spencers]

but it was EQUILIBRIUM ...plus there was no change in temp, pressure or concen. of any reactants and no catatlyst to increase the rate ....i dont knw but i wrote conc. remains equal on both sides of the equation
the reduction potential just tels us if the reaction (forward) is feasible or not

If you noticed in the data booklet, the equations of the reduction potentials are all reversible, i.e, they show you it is an equilibrium, it's just that the more positive the value of the reduction potential is, the more the reaction moves towards the right. That's why the reduction potential of say, flourine, is much more positive than that of magnesium for example, because magnesium ions tend to accept electrons (hence equilibrium is more to the left) than gain them.

 

[Marks&Spencers]

dnt freak out ...we dnt knw yet which answer is correct ....if anyway u got it wrong ..i am sure u'll get awarded for the method

Yeah I guess you're right. It was 2 marks or something. I'm glad I'm just done with chemistry anyway.

 

[Thampi4]

If you noticed in the data booklet, the equations of the reduction potentials are all reversible, i.e, they show you it is an equilibrium, it's just that the more positive the value of the reduction potential is, the more the reaction moves towards the right. That's why the reduction potential of say, flourine, is much more positive than that of magnesium for example, because magnesium ions tend to accept electrons (hence equilibrium is more to the left) than gain them.

I couldn't put it in a better way.. Nice work

 

[Thampi4]

Ok can you please explain to me how you got that 25? You seem like a smart person and I didn't get that answer so now I'm kind of freaking out. I got 2.5 x 10^9. I know it's a big number but I checked it a million times and this is how I got it. I did it the same way another poster on this thread did it.

Ok

The concentration of both the iron ions were the same, because they both hav same mole ratio
The conc of I- is 2x concentration of I2 because their mole ratio was 2 to 1

 

[Thampi4]

Substitute it in ur Kc equation and ull get 25
The iron ions cancel out

 

[Thampi4]

So it's (1x10^-2)/(2x10^-2)^2. Whis is 25

 

[Thampi4]

Yeah I guess you're right. It was 2 marks or something. I'm glad I'm just done with chemistry anyway.

I think the gt will be around 60-65

 

[Marks&Spencers]

I think the gt will be around 60-65

I sure do hope so! Hopefully we'll all do well. Anyway thank you so much now I'm much more relieved. You have physics tomorrow so I'll leave you to study now. Good luck!

 

[queen of the legend]

If you noticed in the data booklet, the equations of the reduction potentials are all reversible, i.e, they show you it is an equilibrium, it's just that the more positive the value of the reduction potential is, the more the reaction moves towards the right. That's why the reduction potential of say, flourine, is much more positive than that of magnesium for example, because magnesium ions tend to accept electrons (hence equilibrium is more to the left) than gain them.

yup i guess that was a silly mistake ...anyhw thx

 

[Marks&Spencers]

yup i guess that was a silly mistake ...anyhw thx

Don't worry. It was only worth a mark! Hopefully it'll be one of the few ones lost. Focus on the rest of your studies now

 

[vivo990]

Ok can you please explain to me how you got that 25? You seem like a smart person and I didn't get that answer so now I'm kind of freaking out. I got 2.5 x 10^9. I know it's a big number but I checked it a million times and this is how I got it. I did it the same way another poster on this thread did it.

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.

 

[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..!