Chemisty C2 - 2015 UNOFFICIAL Markscheme

Reply 40

RKM21

3

Whats the point of this now guys? Ik its good for assurance but lets move on!

Reply 41

hanna-gm

[QUOTE="neil20143;55802315"]Hi :smile:

I tried to make an unofficial mark scheme for this. Please be free to add things :smile:

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)[/QUOTE

for 5a does it have to be silver nitrate ?? I put silver chloride and then calcium carbonate? ]

Reply 42

nv1234

For the one about surface area increasing rate of reaction....

I put there are more points of contact but I did not write anything about successful collisions, does that count?

Reply 43

neil20143

OP

4

Original post by RKM21

Whats the point of this now guys? Ik its good for assurance but lets move on!

Exactly, you just answered your own question :smile:

Reply 44

neil20143

OP

4

Original post by nv1234

For the one about surface area increasing rate of reaction....

I put there are more points of contact but I did not write anything about successful collisions, does that count?

Generally successful collisions is always a side comment for an extra Mark in C2 so it's not a bad thing at all if you didn't write it.

Reply 45

Veltex

In the C3 paper on the first page I wrote the name of the elements instead of their symbols. Do you guys reckon I'll get the marks?

Reply 46

11Jason11

4

http://www.thestudentroom.co.uk/showthread.php?t=3327275&p=55803793#post55803793 --OFFICIAL THREAD AQA GCSE P2 & P3 Wednesday 20th May 2015

Reply 47

Muaaz98

9

Original post by neil20143

Hi

I tried to make an unofficial mark scheme for this. Please be free to add things :smile:

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)

Wow Thanks so much for this! Looks like I probably got around 54/55 then, wish I didn't miss that stupidly easy balancing equation question!! :angry:

Reply 48

neon_reaper

7

Original post by neil20143

Hi

I tried to make an unofficial mark scheme for this. Please be free to add things :smile:

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)

2)a)i) could also have had effervescence (bubbling)
2)c) I believe the main points were: directly proportional up to 0.7dm3, no change after 0.7dm3 and anomaly for third experiment. Obviously had to expand and explain to get the full 6.
3)c) I'm pretty sure they just wanted that its a smart metal, or the temperature of the mouth will maintain the shape etc. because smart metals are directly referenced in the spec (don't think you can just have hard/strong which is what i put :frown:

3)c)ii) You could have it is too soft, too easily deformed etc and it would corrode
4)a) I think you would have to say the relative masses to get the marks (proton, neutrons = 1, electrons = 1/1840 or negligible)
5)b) i think alkali could have been an answer, but base is the much safer answer
6)d)iii) Liquid iodide has no free moving electrons and it is not ionic therefore there is nothing to transport charge through the substance

Well Done and thank you for making this, keep it up :smile:

Reply 49

#sarahsmith2

7

Has anyone made a C3 one??

Reply 50

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.

Reply 51

ladyrailly

2

From the mark schemes being published here I've got 39... which is fine because I'm not doing any sciences at college so I'm pretty happy about that :smile:

C3 on the other hand...

Hopefully C1 brings my grade up because all of the unit 1 exams are really easy

oh, and for the empirical formula question I worked everything out correctly but ended up with Pb3O4.5 so instead of simplifying that I rounded O up to 5 so i ended up with Pb3O5 :mad:

(edited 8 years ago)

Reply 52

Petroleum99

Original post by #sarahsmith2

Has anyone made a C3 one??

No I havnt seen one around yet. I found the test quite easy to be honest, except for the 5mark question and the last question.

Is there a C3 one?

Original post by RahulKOfficial

For improvements for the experiment I wrote use a data logger instead of a thermometer. Do you think that will be right?

Btw Rahul what was ur answer for how solid lead is obtained from lead nitrate?

Reply 55

ARiley1765

7

Original post by ladyrailly

From the mark schemes being published here I've got 39... which is fine because I'm not doing any sciences at college so I'm pretty happy about that :smile:

C3 on the other hand...

Hopefully C1 brings my grade up because all of the unit 1 exams are really easy

oh, and for the empirical formula question I worked everything out correctly but ended up with Pb3O4.5 so instead of simplifying that I rounded O up to 5 so i ended up with Pb3O5 :mad:

Wait so my c1 exam could improve my c2 exam. Even though they are separate GCSE's or what if you do one higher and the other foundation?

Reply 56

Mina_

8

Isnt 5c1) filtration ?

Reply 57

ladyrailly

2

Original post by ARiley1765

Wait so my c1 exam could improve my c2 exam. Even though they are separate GCSE's or what if you do one higher and the other foundation?

They're separate units but at least at my school they all add up to become a general Chemistry GCSE along with Biology and Physics. I think the marks will be more important than the grades (because of the difference in grades between foundation and higher) - they'll add all the marks up and then form a grade from that I think. I'm pretty sure C1 can improve your mark :smile:

Reply 58

ladyrailly

2

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:

Reply 59

Petroleum99

Can anyone explain this empirical formula question, in so confused how you can get these figures ....

Chemisty C2 - 2015 UNOFFICIAL Markscheme

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