C7 OCR 21st Century Science 2016 Exam 22/06/16

Reply 20

babznd

Original post by Em14520

So did I !!!

There is so many different answers :biggrin:

Reply 21

niamhdoesmaths

21

First question about differences in processes of making fertilisers and drugs:
Fertilisers need to be made on a large scale as they are bulk and millions of tonnes of them are used
Drugs need to be very pure as they need to be safe for human consumption

There were 4 different dyes used

A locating agent is needed as some chemicals aren't visible to the naked eye and so this helps them to be seen (possibly wrong though)

I think the amount of dye C was the highest as it had the highest peak frequency and longest retention time?? I'm very unsure of this though

Alex could use the graph results and the results of known chemicals because he can cross-reference the two to find out what combination of known chemicals are in the sweet (I think)

The measurements needed are the distance between the start line and the centre of the spot, and the distance between the start line and the solvent front.

If I remember more I'll post them

Reply 22

babznd

Original post by NiamhM1801

First question about differences in processes of making fertilisers and drugs:
Fertilisers need to be made on a large scale as they are bulk and millions of tonnes of them are used
Drugs need to be very pure as they need to be safe for human consumption

There were 4 different dyes used

A locating agent is needed as some chemicals aren't visible to the naked eye and so this helps them to be seen (possibly wrong though)

I think the amount of dye C was the highest as it had the highest peak frequency and longest retention time?? I'm very unsure of this though

Alex could use the graph results and the results of known chemicals because he can cross-reference the two to find out what combination of known chemicals are in the sweet (I think)

The measurements needed are the distance between the start line and the centre of the spot, and the distance between the start line and the solvent front.

If I remember more I'll post them

Could you say dye c had the biggest surface area and peak? :smile:

Reply 23

BULL14

16

Original post by babznd

Could you say dye c had the biggest surface area and peak? :smile:

It was three dyes

Reply 24

BULL14

16

Original post by NiamhM1801

First question about differences in processes of making fertilisers and drugs:
Fertilisers need to be made on a large scale as they are bulk and millions of tonnes of them are used
Drugs need to be very pure as they need to be safe for human consumption

There were 4 different dyes used

A locating agent is needed as some chemicals aren't visible to the naked eye and so this helps them to be seen (possibly wrong though)

I think the amount of dye C was the highest as it had the highest peak frequency and longest retention time?? I'm very unsure of this though

Alex could use the graph results and the results of known chemicals because he can cross-reference the two to find out what combination of known chemicals are in the sweet (I think)

The measurements needed are the distance between the start line and the centre of the spot, and the distance between the start line and the solvent front.

If I remember more I'll post them

It was three dyes

Reply 25

Speedbird129

12

Original post by Jashi1999

Nah Im sure its -547

I also got -547 even though some got -587.

Reply 26

Speedbird129

12

Original post by BULL14

It was three dyes

I also put three dyes as three were in the three substances.

Reply 27

niamhdoesmaths

21

Original post by BULL14

It was three dyes

What do you mean by 'three dyes'?

Reply 28

Dr Dead Trim

OP

Original post by Carmenh

How did everyone find that? I'm so mad at myself. I revised so hard, and I got As and A*s in the past papers, but when it got down to the actual exam, I didn't finish it! I didn't finish the last double spread page, which was 7 marks :frown:

and it looks like I've made a lot of mistakes in the parts I did do. This is probably the worst exam I've done so far. It wasn't even that difficult in retrospect. Ugh...

really i found it surprisingly easily except the vertical condenser question which i eventually figured out anyway i hope the best for you

Reply 29

Username1502

12

Original post by NiamhM1801

First question about differences in processes of making fertilisers and drugs:
Fertilisers need to be made on a large scale as they are bulk and millions of tonnes of them are used
Drugs need to be very pure as they need to be safe for human consumption

There were 4 different dyes used

A locating agent is needed as some chemicals aren't visible to the naked eye and so this helps them to be seen (possibly wrong though)

I think the amount of dye C was the highest as it had the highest peak frequency and longest retention time?? I'm very unsure of this though

Alex could use the graph results and the results of known chemicals because he can cross-reference the two to find out what combination of known chemicals are in the sweet (I think)

The measurements needed are the distance between the start line and the centre of the spot, and the distance between the start line and the solvent front.

If I remember more I'll post them

Confirmation of these answers (idk if this is needed but I'm bored and am avoiding P7 so..)

Yes, there were indeed 4 dyes -- that's also what I got.
Yeah -- a locating agent is used in order to identify spots of chemicals on a chromatogram which are otherwise not visible.
Dye C was, in fact, the most used chemical in the sweet as it had the highest peak height. Retention time is irrelevant to this question I think.
Yeah -- basically the known-substance chromatography data can be used as 'standard reference material (SRM)' in order to identify and cross-compare with the actual data the person obtained.
Yeah and the measurements required are the distance traveled by the solvent front and also the distance that the spot has traveled.

Reply 30

BULL14

16

Original post by Username1502

Confirmation of these answers (idk if this is needed but I'm bored and am avoiding P7 so..)

Yes, there were indeed 4 dyes -- that's also what I got.
Yeah -- a locating agent is used in order to identify spots of chemicals on a chromatogram which are otherwise not visible.
Dye C was, in fact, the most used chemical in the sweet as it had the highest peak height. Retention time is irrelevant to this question I think.
Yeah -- basically the known-substance chromatography data can be used as 'standard reference material (SRM)' in order to identify and cross-compare with the actual data the person obtained.
Yeah and the measurements required are the distance traveled by the solvent front and also the distance that the spot has traveled.

I am pretty sure it was 3 dyes.

What did you write for the six marker about concentration and strength of the acids?

also the last six marker?

Reply 31

Dr Dead Trim

OP

Original post by BULL14

Shall we make a full mark scheme?

For the bonds energy for come reason I got 40kj :frown:

Yeah im trying but i forgot all the questions

and the reason why you got 40 is because on the left hand side you times everything by 2.

This was probably a misconception as there was 2 hydrogen atoms and 2 flourine atoms so you probably thought there were two H-H and two F-F bonds where in reality there was only one of each.

You would have got something like H-H = 432 so 2 x 432 = 864
then for F-F = 155 so 2 x 155 = 310

add them together 864 + 310 = 1174

this was your sum of bond energy for the reactants minus the bond energy on the other side which was 1134 leaving you with 40

Hope this helped

Reply 32

Dr Dead Trim

OP

Original post by NiamhM1801

First question about differences in processes of making fertilisers and drugs:
Fertilisers need to be made on a large scale as they are bulk and millions of tonnes of them are used
Drugs need to be very pure as they need to be safe for human consumption

There were 4 different dyes used

A locating agent is needed as some chemicals aren't visible to the naked eye and so this helps them to be seen (possibly wrong though)

I think the amount of dye C was the highest as it had the highest peak frequency and longest retention time?? I'm very unsure of this though

Alex could use the graph results and the results of known chemicals because he can cross-reference the two to find out what combination of known chemicals are in the sweet (I think)

The measurements needed are the distance between the start line and the centre of the spot, and the distance between the start line and the solvent front.

If I remember more I'll post them

thanks i gave you a shoutout for this

Reply 33

Dr Dead Trim

OP

Original post by BULL14

I am pretty sure it was 3 dyes.

What did you write for the six marker about concentration and strength of the acids?

also the last six marker?

the question specified identify how many Different dyes there are there were 4 spots 2 of had the same retardation or retention factor so this only counted as 1 different dye rather than 2

Reply 34

Dr Dead Trim

OP

Original post by babznd

Could you say dye c had the biggest surface area and peak? :smile:

possibly because dye c had the biggest peak but defo not for surface area

Reply 35

MezmorisedPotato

18

I am quite sure it was four dyes.

Reply 36

niamhdoesmaths

21

Original post by Username1502

Confirmation of these answers (idk if this is needed but I'm bored and am avoiding P7 so..)

Yes, there were indeed 4 dyes -- that's also what I got.
Yeah -- a locating agent is used in order to identify spots of chemicals on a chromatogram which are otherwise not visible.
Dye C was, in fact, the most used chemical in the sweet as it had the highest peak height. Retention time is irrelevant to this question I think.
Yeah -- basically the known-substance chromatography data can be used as 'standard reference material (SRM)' in order to identify and cross-compare with the actual data the person obtained.
Yeah and the measurements required are the distance traveled by the solvent front and also the distance that the spot has traveled.

Oh wow that's good as most of these were guesses! :colondollar:

Original post by BULL14

I am pretty sure it was 3 dyes.

What did you write for the six marker about concentration and strength of the acids?

also the last six marker?

There were 4 rows of ink spots, so I assumed that meant 4 different dyes. Trust me there were definitely 4 rows, I counted 3 times!!
For the one about concentrations and pH, I basically just stated whether each acid was strong, medium or weak because of the pHs, and then for the concentrations, those that took a higher volume of alkali to neutralise them I said were more concentrated, and vice versa.
For the one about bonds I found that in the diatomic molecules there was a pattern between chlorine, bromine and iodine (which gets less as you go down the group) which supported Len's idea, however fluorine didn't fit as it had a lower bond energy than chlorine so this didn't support his idea. Then for the one concerning halides, I noticed there was the patten between HF, HBr and HI, which supported his idea, however HCl was the odd one out which didn't support him, as it is lower than both HF and HBr. I used the numbers from the table too.

Original post by Dr Dead Trim

thanks i gave you a shoutout for this