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OCR Salters Chemistry of Materials 2849

i've been improving in past papers too but you never know what can come up! hopefully stuff like colorimetry and thin layer chromatography come up which i have a feeling will come up. Good luck everyone!!!!

Reply 21

Calv

yer... same as kash786
hopefully we hv long q in colorimetry, chromatography n ligands!!!

3 more hrs until our exam!!! GOOD LUCK!

Reply 22

kitty123

1

Oh no I keep doing rubbish on past papers! :frown:

What grade was 65/90 if you don't mind me asking? I'd be happy with that!

Reply 23

kashkash786

65/90 would be very close to an A depending on the grade boundaries this year, as they sometimes go as low as 63/90!

Reply 24

lil_dreamer90

best of luck guys :biggrin:

i hope the boundries are low.. at most i can get 66/90 on practise papers.. they are so picky about the wording you use! good luck :biggrin:

Reply 25

james s

7

Only a few hours to go... I've given up on working through past papers, am reading through paper & mark scheme at the same time to see how they want the answer written, as I know the stuff, but miss out the specific wording some of the time =/

Good luck!

Reply 26

RosiePosiePuddingAndPie

12

EEK! I'm scared!
Three A's last year, then an E in 2849 this year! I hate this exam! I don't seem to be able to get any higher than 60/90 in past papers, which is rubbish :frown:

Reply 27

kashkash786

Let's do some quick summaries here! For example,

acid + alcohol = ester + water

a condensation reaction using moderately concentrated sulphuric acid and heat under reflux. You can use the same reagents for the reverse reaction to hydrolyse an ester link.

To hydrolyse a secondary amide link in a protein, use moderately concentrated hydrochloric acid and heat under reflux for acid hydrolysis.

For alkaline hydrolysis use moderately concentrated sodium hydroxide and heat under reflux.

We can help each other by giving each other tips like these.

Colorimetry

1. Select a filter with the complimentary colour to the solution being test.
2. Zero the colorimeter with a cuvette of distilled water.
3. Make a up a range of solutions of the known concentration and measure the absorbance of these solutions.
4. Plot a calibration curve (absorbance vs concentration)
5. Measure the absorbance of the unknown solution and then finally find the concentration of the unknown solution by reading it off of the calibration curve.

Another tip, always remember only temperature will affect Kc!

Reply 28

Calv

wow, the paper is easier than i expect!!!
chromatography
protein
ligands q are alright!

cant believe they r so similar to those past papers!!!

did u get 54.3% ish in that 5 marks maths q?
did u use chlorine to oxidise iron?

x

Reply 29

bobbiebuddha

I got 54.3% for the maths question. However, I didn't use chlorine to oxidise the iron, I used the other one (can't remember what it was).

Reply 30

mentally-guitarded

yeah, the paper was awesome. yeah i got 54.3 % and used chlorine to oxidise because it had a more positive E. I got first order for the rate and s-1 for the units. The chromatography question and keratin one was a gift.

Reply 31

RosiePosiePuddingAndPie

12

I think I must be stupid, because I found that paper really hard :frown:

Couldn't do the 5 mark calculation, and completely forgot the rust equations, amongst other things. Bad times.

Reply 32

kitty123

1

RosiePosiePuddingAndPie

I think I must be stupid, because I found that paper really hard :frown:

Couldn't do the 5 mark calculation, and completely forgot the rust equations, amongst other things. Bad times.

Don't worry you're not the only one I found it sooo difficult I left out the 5 mark calculations and the equation for rust. I thought zinc had the more positive E cell? Thats why I put it down but apparently it was chlorine :s-smilie:

Another 3 marks down the drain. How about whether the compound(amino acid i think) would be acid alkali or neutral? Did anyone put neutral as they form zwitter ions?

Reply 33

dbox

kitty123

Don't worry you're not the only one I found it sooo difficult I left out the 5 mark calculations and the equation for rust. I thought zinc had the more positive E cell? Thats why I put it down but apparently it was chlorine :s-smilie:

Another 3 marks down the drain. How about whether the compound(amino acid i think) would be acid alkali or neutral? Did anyone put neutral as they form zwitter ions?

I put alkali, because although the zwitterion won't contribute or remove any H+ ions overall, there was another EDIT:amiNE group which would protonate and act as a base.

I did have a bit of a brainstorm when trying to remember whether butane meant a 3-C or a 4-C compound (luckily in the end I went for 4). And I think you'd use chlorine since it has a more positive E (so the total Ecell is positive).

edit: oh, and the NMR question confused me. I put that it was for propan-2-ol, mainly because propan-1-ol has 4 (?) proton environments, but also because the ratio (6:1:1) for propan-2-ol seemed to be the one shown on the diagram. Good thing the whole thing was only 2 marks though, cause I couldn't account for the middle peak (I seem to remember it should have been R-RCH-R, but the shift didn't match up).

Reply 34

kitty123

1

dbox

I put alkali, because although the zwitterion won't contribute or remove any H+ ions overall, there was another amide group which would protonate and act as a base.

I did have a bit of a brainstorm when trying to remember whether butane meant a 3-C or a 4-C compound (luckily in the end I went for 4). And I think you'd use chlorine since it has a more positive E (so the total Ecell is positive).

I have completely failed :frown:

I must have read it wrong then, I could have swore zinc was the more positive one :frown:

Reply 35

kashkash786

I gotta say that was a challenging paper, but optimistically i would say it was ok, and in my opinion it went better than in january in which i got an E and hopefully in this test i should've got a minimum of a C which i would be happy with! Some tough questions were the calculations for the 5 mark which i just totally misread, and the initial rate of reaction one which i also found difficult. Hopefully the test went well for everyone! Good luck for Chemistry by Design!

Reply 36

mentally-guitarded

I got the zwitterion one wrong.. i put neutral. But i think i might get a mark since i put that the COO- and NH3+ interact. I put propan-2-ol for the NMR because the ratio of H in the R-CH3 to R-OH was 6:1, confirmed this by measuring the actual heights.

Reply 37

dbox

kitty123

I have completely failed :frown:

I must have read it wrong then, I could have swore zinc was the more positive one :frown:

I could be wrong about that amine group thing though. And how many marks was that electrode potential question anyway? I reckon you should be able to get at least half marks if you talked about the Fe(III) ions being reduced/accepting electrons or whatever (I can't remember which way round it was on the paper).

Reply 38

mentally-guitarded

The electrode potential one was 3 i think.

Reply 39

RosiePosiePuddingAndPie

12

dbox

I put alkali, because although the zwitterion won't contribute or remove any H+ ions overall, there was another EDIT:amiNE group which would protonate and act as a base.

I did have a bit of a brainstorm when trying to remember whether butane meant a 3-C or a 4-C compound (luckily in the end I went for 4). And I think you'd use chlorine since it has a more positive E (so the total Ecell is positive).

edit: oh, and the NMR question confused me. I put that it was for propan-2-ol, mainly because propan-1-ol has 4 (?) proton environments, but also because the ratio (6:1:1) for propan-2-ol seemed to be the one shown on the diagram. Good thing the whole thing was only 2 marks though, cause I couldn't account for the middle peak (I seem to remember it should have been R-RCH-R, but the shift didn't match up).

Oh poo, I put neutral! Your point makes sense though.

That was one of the few things I could cope with - Magical Elephants Pop Bubblegum (Methane Ethane Propane Butane!) :p:

I need my chemistry in simple terms lol!!!

And I put the same as you, because of the amount of environments, but I couldn't account for one of them either, so I just crossed out the start of that sentence and pretended that I'd never set out to show it :redface:

Wish I'd thought of showing the ratio though lol!

OCR Salters Chemistry of Materials 2849

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