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OCR Salters Chemistry 2849 - Chemistry Of Materials

Reply 80

W0nker

8

I got 2 but i've heard more 3's.

Reply 81

Eliminos

From wikipedia:

a linear plot for a first order reaction is obtained from ln([A]) vs time
a linear plot for a second order reaction is obtained from 1/[A] vs time

If we assume the Y axis was concentration, even though it was mass, as the two are linearly interchangable. A mass of 1g could have been 1mol dm^-3 and a mass of 0.5g could be 0.5mol dm^-3

So, the four points I can definitely remember are:

mass | time
1.........0
0.5......3600
0.25.....7400
0.0625..14400

A replicaiton of the graph we saw is:

A plot of ln(conc) vs time (remember, this should come up as a linear plot):

A plot of 1/conc vs time

The middle graph looks pretty linear to me, more so than the last one. The reaction was first order, or if we want to put a number to it it was probably around order 1.05. It was not second order.

I'm trying not to act like a dick about this, but I'm just proving to HorrowShow that I am not 'totally wrong'

Reply 82

hitman012

I said something about it opposing the increase in concentration of H+ by producing more of the ester linkages. It was pretty much in the same vein as your response.

Reply 83

username68316

3

hitman012

I got 3 for the chiral carbons. If anyone can remember the chemical name, we could look it up and see.

i cant remember the chemical name. what i did to the skeletal formula was to add dashed lines where the hydrogen atoms came off, so i could tell in my mind what had 4 different groups. the three chiral centres for me were on the right hand side, not next to a double bond. Besides, you're going to imperial, so you must be right :p:

Reply 84

hitman012

Yeah, I did the same as you adding the lines and got the same result :smile:

Reply 85

W0nker

8

Eliminos, Bloody hell you're excited lol,

Maybe horrorshow said his teacher said it was 2nd order just to shut people up lol.

Reply 86

eliana

what did people but for the more positive half cell out of Ni and Cd and why?

Reply 87

hitman012

Cd had the more positive electrode potential, i.e. it was accepting electrons from the Ni half-cell.

Reply 88

Eliminos

Einsteinium

Eliminos, Bloody hell you're excited lol,

Maybe horrorshow said his teacher said it was 2nd order just to shut people up lol.

1) The Internet is serious business
2) I take being told I am totally wrong to heart, I wanted to prove myself
3) I'm trying to procrastinate around decision maths revision. If someone would like to still say its second order, I'll try and prove it a 3rd way if you like :biggrin:

Reply 89

username68316

3

So the Ni was the negative half cell supplying the electrons via the external circuit

Reply 90

anotherarunan

7

what was the last part of the last question on the paper about...with the red/brown colour on the map! i hated the whole of the last question in general!

Reply 91

Eliminos

atgooner

what was the last part of the last question on the paper about...with the red/brown colour on the map! i hated the whole of the last question in general!

I said the copper ion is reduced forming copper metal which accounts for the browny colour. The sulphur in the SO2 is oxidised and the lost electrons go to reducing the copper. The reaction is a redox reaction.

Reply 92

W0nker

8

Yes, cadnium postive electrode.

Reply 93

hitman012

Eliminos

I said the copper ion is reduced forming copper metal which accounts for the browny colour. The sulphur in the SO2 is oxidised and the lost electrons go to reducing the copper. The reaction is a redox reaction.

Yeah, I put that the sulphur reaction has the lower electrode potential, so it reduces the Cu2+ ion in the complex to a red/brown Cu(s).

Reply 94

anotherarunan

7

got that one wrong too then..

Reply 95

pinkrules

ahh for that graph of half life or whatever i put second order first cause the time didint double then i didnt a different reading then it did double so i changed it all! ahh crazy!
hopefully the examiner markin it will add on some more marks cause one way or another i had 1 of the 2 corect answers lol

Reply 96

bband

1

In the Optical Isomerism question, When they asked you to draw the two enantomers, did you have to draw the all the side groups as well?
Did you put C6H5 on one of the carbons?

Reply 97

Scott Storch

1

How many marks is an a?

Reply 98

hitman012

I condensed the side group into C7H7 or whatever it was and had that as a separate side chain. I expect that as long as it's clear that you understand the principle of the mirror image, you will get the mark.

And looking at past examiners' reports, an A has ranged from 62-72 out of 90. It all depends on how difficult the examiners think the paper is in relation to the past several.

Reply 99

anotherarunan

7

hitman012

I condensed the side group into C7H7 or whatever it was and had that as a separate side chain. I expect that as long as it's clear that you understand the principle of the mirror image, you will get the mark.

And looking at past examiners' reports, an A has ranged from 62-72 out of 90. It all depends on how difficult the examiners think the paper is in relation to the past several.

how hard do u think it was then? i thought it was pretty tough compared to the other papers.

OCR Salters Chemistry 2849 - Chemistry Of Materials

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