Chemisty C2 - 2015 UNOFFICIAL Markscheme

How did u get 5624 as his cardiac output? i got 3232 or something

I'm pretty certain 5624 is correct.

Can somebody post the possible points for the six marker?

If it's the sodium thiosulphate concentration question that you're regarding to then:

-As concentration increased so did gas produced to a certain extent? if that's the other variable can't remember now.

-This is because there's more particles of Sodium thosulphate for zinc to react with so more gas produced.

-At 0.7 concentration and afterwards there was no increase in gas production, i.e the reaction has stopped.

-This is because all the zinc would be reacted (reactant) with the acid and increasing the concentration just meant the additional sodium thiosulphate particles have nothing to react with.

on the empirical formula i got pbo6 isn't that the same as pb2o3 - thanks for the mark scheme too dude

I predict 47 for A* 40 for A in both papers. I found them hard but people generally found it quite easy and they were actually quite simple looking back. Does anyone have the C3 unofficial Markscheme or can make one?

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

(I'm not sure about this question)

Isn't the answer to 6(d) (iii) Because it has no free electrons able to carry charge due to them being used in the covalent bond?

most people in twitter found c3 hard and my school found it hard even though i found it decent, it won't be 47+ for c3 definitely not, i think maybe 45, lol 2013 b3 paper biology 36 for an a* and that was paper was so easy hence why i think this (as it's based on how the whole country does).

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

(I'm not sure about this question)

do u have the 6 markers answers yet?
also so far from the unofficial mark scheme you have produced i have got 41/60 what grade do u think that would be?