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# Chemisty C2 - 2015 UNOFFICIAL Markscheme watch

1. Also for 5c I have absolutely no clue why I put distillation, I revised filtration loads too, I think I was rushing in the last 15 minutes and it was the first thing I thought of D:
2. Can anyone explain this empirical formula question, in so confused how you can get these figures ....
3. did anyone else think this paper was rubbish!?
4. (Original post by ellefrancessa)
did anyone else think this paper was rubbish!?
I thought it was quite easy just some stupid questions.
5. (Original post by ellefrancessa)
did anyone else think this paper was rubbish!?
One of the worst papers I've seen I felt like it was so biased for some reason..
6. (Original post by Petroleum99)
How on Earth did you get Pb2O3? I divided by the mass they gave us by the atomic mass of the element which was given and got a ratio of 0.03 for lead and 0.045 for oxygen. So I simplified it down to Pb015.
Mass: 6.21 | 0.72
Ar: 207 | 16
Divide: 0.03 | 0.045
Ratio: 1 | 1.5

Then you multiply the ratio by 2 because you can't have 1.5 as a ratio therefore it is 2:3

What you forgot to do is 0.045 divided by 0.03 to give yourself the ratio
7. OH MY GOD I just realised I missed out that balancing question!?!?!
8. (Original post by ARiley1765)
One of the worst papers I've seen I felt like it was so biased for some reason..
It all seemed to be on bonding! I know I've done terrible.. I didn't have time to answer half the questions. So glad I dropped triple and moved to double so biology and physics can pull my grade up hahah. Thank god for an A* in my ISA too!
9. (Original post by Mina_)
Mass: 6.21 | 0.72
Ar: 207 | 16
Divide: 0.03 | 0.045
Ratio: 1 | 1.5

Then you multiply the ratio by 2 because you can't have 1.5 as a ratio therefore it is 2:3

What you forgot to do is 0.045 divided by 0.03 to give yourself the ratio
Oh my god I can't believe I made that mistake. As a triple scientist aswell I'm disappointed. Thank you anyway
10. (Original post by Mina_)
Mass: 6.21 | 0.72
Ar: 207 | 16
Divide: 0.03 | 0.045
Ratio: 1 | 1.5

Then you multiply the ratio by 2 because you can't have 1.5 as a ratio therefore it is 2:3

What you forgot to do is 0.045 divided by 0.03 to give yourself the ratio
I did this apart from the last step- how many marks do you reckon that would be?
11. can anyone give the main points that they will be looking for on the 6 marker?
12. (Original post by OpTic Crimbot)
Evaporating and condensing
13. (Original post by ARiley1765)
One of the worst papers I've seen I felt like it was so biased for some reason..
It all seemed to be on bonding! I know I've done terrible.. I didn't have time to answer half the questions. So glad I dropped triple and moved to double so biology and physics can pull my grade up hahah. Thank god for an A* in my ISA too!
14. (Original post by Emma_B1)
I did this apart from the last step- how many marks do you reckon that would be?
Probably 3 out of 4, I wouldn't worry tbh
15. [QUOTE=neil20143;55802315]Hi I tried to make an unofficial mark scheme for this. Please be free to add things

1a. State one conclusion about the effect of temperature on the rate of reaction? (1 mark)
-An increase in temperature increases the rate of reaction

aii. One reason why? (1 mark)
-Because the volume of gas being produced at 40 degrees was more rapid than at 20 degrees.

a(iii). Average rate (1 mark)
-2 cm cubed per second (I think)

1 (b) two students should the student keep constant? (2 marks)
-Mass of Marble Chips
-Concentration of acid

b ii. Increasing the surface area affect the rate of reaction? (2 marks)

-Increases the rate of reaction
-As the particles are colliding more frequently (more successful collisions)

c. Why does a catalyst reduce costs?
-Because less energy is needed to start the reaction (as it has a lower activation energy)

(there may be alternatives)

2 (a). What could the student see? (1 mark)
-Copper being formed (brown) or zinc disappearing

2(b).Improves the investigation? (2 marks)
Improvement: Use a lid/ insulate the container
Reason: Prevents heat from being transferred to the surroundings/escaping.

2c (6 marker - will do later at some point)

3 (a). How does a metal conduct electricity? (4 marks)
-Delocalised electrons can move through the metal
-Transfer electrical charge
-Sea of moving electrons (structure)
-Lattice of positive ions (structure)

3(b). Describe the structure of an alloy is different to a metal (2 marks)
-Different elements with different sizes
-Distort layers in the mixture, preventing them from sliding over each other.
OR
-Irregular pattern of atoms.

3(c). Why is Nitinol used in braces? (1 mark)
-Hard/strong/corrosive-resistant/smart-alloy

3(c) (ii). Why are coins not made out of pure copper? (1 mark)
-Because it is too soft so will corrode

3 (c) (iii)). Aluminium Oxide

3 (c) (iv). How can the reaction produce two different products? (1 mark)
-Made using different reaction conditions / any specified reaction condition (e.g. pressure, temperature).
-Using different catalysts

3(d). Instrumental methods are used to detect impurities? (2 marks)
Any two from:
-They use very little samples.
-Accurate
-Sensitive
-Fast

4 (a). Why does Lithium have 7 as it's atomic number? (3 marks)
-3 protons
-4 neutrons
-3 + 4 = 7 which is its mass
-electrons have a very small mass.

4(b). Complete the sentences (2 marks)
-Grams
-Carbon-12

4(c). Isotope differences (3 marks)
-18-Oxygen had 2 more neutrons than 16-Oxygen
-Same number of protons
-Same number of electrons

5 (a). Name a soluble compound that contains silver
(1 mark)
-Silver Nitrate

5(a) ii Compound containing carbonate ions (1 mark)
-Potassium or Sodium Carbonate

5(b) (1 mark)
-(insoluble)Base

5(c) (i). State how lead nitrate can be obtained from lead nitrate oxide (1 mark)
-Crystalisation
-Evaporate and leave to dry.

5c(ii) (1 mark)

Pbo + 2HNO3 = PB(NO3) + H2O

5c (iii). number of atoms in the compound
-9

5(d). Empirical Formula (4 marks)
Pb2O3

6(a). Structure and bonding in sodium chloride (4 marks)
-Ionic Bonding
-Sodium atoms lose one electron to form positive ions
-Chloride ions gain one electron to form negative ions
-Opposites attract
-Giant ionic structure
-Cubic Lattice
-Electrostatic forces

Any of these should get the mark I think

6(b). Other products when brine is electrolysed (2 marks)
-Sodium Hydroxide
-Hydrogen

6(c). Ethical reason for not putting Iodine in food (1 mark)
-People may not want to have these extra Iodine amount (no choice)

6(d) (i). (2 marks)
-3 electrons lone pairs and one covalent bond

6(d) (ii). Why does Iodine have a low melting point (3 marks)
-Simple molecules
-Weak intermollecular forces
-Little energy needed to break them down

6(d) (iii). Why does iodine not conduct electricity? (2 marks)
-No overall charge so can't carry electrical charge

How come the answer for the empirical formula is Pb203? I got Pb02 and the majority of my year got that...
16. (Original post by electrahearts)
OH MY GOD I just realised I missed out that balancing question!?!?!
It was only 1 mark, you'll be fine Unless you mean the entire question and not just that specific part, in which case good luck with that

(also nice icon )
17. Are u able to do a similar one for the B2 test?
18. (Original post by eza11)
for 4b) I put moles and carbon-12?? Was it just me that didn't put grams?
I PUT MOLES TOOO!!
19. (Original post by Petroleum99)
Can anyone explain this empirical formula question, in so confused how you can get these figures ....
so basically people are a'l caught up in the 'you've gotta round to a whole number stage' like after you did mass divided by Mr for both then divide both outcomes by the smallest outcome, you've gotta round butt some people too thins as like literally round the numbers and others took this as scale them up until they're whole numbers
-hope this helps?
20. (Original post by Palette)
I wrote for the final question that although intermolecular forces in iodine are broken, the covalent bonds between two iodine atoms in an iodine molecule are not broken, meaning there are no delocalised electrons which can carry charge.

Is that valid?
that's exactly what I put, is it right?

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