what are the predicted grade boundaries?
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Chemisty C2 - 2015 UNOFFICIAL Markscheme watch
- 14-05-2015 22:58
- 14-05-2015 23:03
- 14-05-2015 23:18
- 14-05-2015 23:30
Oh good think I've got about 42 not including the 6 marker. Thank you so much this was so useful!
- 14-05-2015 23:35
(Original post by neil20143)
- 14-05-2015 23:40
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.
-Irregular pattern of atoms.
3(c). Why is Nitinol used in braces? (1 mark)
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.
4 (a). Why does Lithium have 7 as it's atomic number? (3 marks)
-3 + 4 = 7 which is its mass
-electrons have a very small mass.
4(b). Complete the sentences (2 marks)
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
5(a) ii Compound containing carbonate ions (1 mark)
-Potassium or Sodium Carbonate
5(b) (1 mark)
5(c) (i). State how lead nitrate can be obtained from lead nitrate oxide (1 mark)
-Evaporate and leave to dry.
5c(ii) (1 mark)
Pbo + 2HNO3 = PB(NO3) + H2O
5c (iii). number of atoms in the compound
5(d). Empirical Formula (4 marks)
6(a). Structure and bonding in sodium chloride (4 marks)
-Sodium atoms lose one electron to form positive ions
-Chloride ions gain one electron to form negative ions
-Giant ionic structure
Any of these should get the mark I think
6(b). Other products when brine is electrolysed (2 marks)
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)
-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
(I'm not sure about this question)
- 15-05-2015 00:01
- 15-05-2015 00:49
For the six mark question, I am pretty sure that the reaction was exothermic because an exothermic reaction can be measured by a rise in temperature. As the concentration increased, the temperature also increased, so i think the reaction is exothermic. An endothermic reaction can be measured by a fall in temperature.Last edited by Uzibear; 15-05-2015 at 00:52.
(Original post by Uzibear)
- 15-05-2015 03:02
For the six mark question, I am pretty sure that the reaction was exothermic because an exothermic reaction can be measured by a rise in temperature. As the concentration increased, the temperature also increased, so i think the reaction is exothermic. An endothermic reaction can be measured by a fall in temperature.
- 15-05-2015 07:13
Being harsh on myself, I lost 10 marks. That's not good at all.
- 15-05-2015 07:14
More grade boundary predictions for C2 and C3?
- 15-05-2015 07:19
C2 I reckon will be quite high, about 47 and C3 will be lower, at about 42
(Original post by JG12333)
- 15-05-2015 09:05
6 (d) iii, I put because there are no free ions to conduct the electricity, pretty confident on that. and for 1 (b) I put the concentration and mass of marble chips. could be wrong though!
- 15-05-2015 09:08
I think i got like 45 according to my marking
- 15-05-2015 09:08
- 15-05-2015 09:46
For the copper one, I said 'Because pure copper is running out' idk
- 15-05-2015 10:41
3c i is because it changes shape when heated in the mouth so pulls the braces into shape with it
- Thread Starter
- 15-05-2015 10:47
- 15-05-2015 11:07
Do you think saying Zinc dissolves instead of disappears is fine?
(Original post by neil20143)
- 15-05-2015 11:10
It depends on the mark scheme They may not even give any marks for the electron transfer and just for the ones you've mentioned (maybe breaking electrostatic forces between the ions point into two seperate marks)
So hopefully my answer was okay