Poll: How many marks did you get?
60-51 (78)
36.79%
50-41 (73)
34.43%
40-31 (43)
20.28%
30-21 (15)
7.08%
20-11 (2)
0.94%
10-0 (1)
0.47%
B0redBrioche
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#1
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#1
Didn't see one which had been made so I'll start
Also this is for AQA C3 Chemistry GCSE 2017 unofficial markscheme and I don't know how to change the thread tile, sorry for unclear title

1)
a) Why does rainwater become hard?
The rainwater runs over rocks and calcium/magnesium ions dissolve into the water making it hard. (2marks)

b) Describe the graph include data
Solubility increases as temperature increases until it reaches 68 degrees (I think) and the solubility decreases as the temperature increases from 68 degrees onwards. Use data points. (3 marks)

c) Adv and Disadv of hard water (2 marks)
Pro- Contains calcium contributing to healthy bones
Con- Bad taste

d) Describe how ion exchange is used to soften hard water
Ion exchange columns contain hydrogen/sodium ions which displace/replace/exchange the calcium ions in the hard water due to the sheer number of them and therefore the calcium ions are removed so the water is softened (3 marks?)

2)
a+b) Tick boxes for overall energy change and formula of methanol (i think) (2 marks)

ci) 6 marker on calorimetry

cii) Make results more accurate
Use a lid or insulate the beaker so less energy is lost to the surroundings (2 marks)

3)
a) Why did M leave gaps?
For undiscovered elements (1 mark)

b) How were elements placed incorrectly?
Some elements were placed in groups with different properties like metals being placed in groups with non-metals e.g. Chromium was in a group with 2 gases (1 mark)

c) Why is fluorine more reactive than iodine?
Less shells so Less shielding so stronger electrostatic forces and so more easily gained the final electron to become stable. (3 marks)

4)
a) 2 Changes between the reaction of water with potassium and lithium
Potassium is more reactive so more effervescence produced, more vigorous reaction and dissolves faster. (2 marks)

b) Titration 5 marker
Measure acid use pipette to squeeze into flask
Put white tile under flask
add few drops of indicator in flask
Use pipette & squeeze the sodium hydroxide or w/e it was into burette and keep adding it until colour change/end point is reached
Swirl the flask while doing it (5 marks)

c) Calculate concentration- 0.21 (3 marks)

d) Precipitate questions
Iron II forms green precipitate (1 mark)
Iodide forms yellow precipitate (1 mark)

5a) Why moderately high temperature used?
Despite being exothermic in the forward direction they use a moderately high temperature to compromise between the yield and the rate of reaction. So high rate of reaction for a smaller yield produces more yield in the long term (3 marks)

b) Increasing the pressure
Increasing the pressure moves the reaction in the direction which produces less gas molecules which is the forward direction so more yield is produced (2 marks)

c) Why high pressure not used? (don't include cost)
Safety issues as it could damage infrastructure or a more complex infrastructure needed which wastes materials (1 mark)

6a)
Calculation question- -81kJ or 81kJ (3 marks)

Describe exothermic in terms of bond breaking and bond forming
Less energy used in bond breaking the then energy released in bond making so it is exothermic. (2 marks)


RANDOM

Balance equations somewhere (2marks)

Why is ethanoic acid have a higher pH?
Less ionising so less H+ ions therefore making it more alkali than HCl at same concentration. (2 marks)

Distinguish between aluminium and magnesium
Aluminium is present if solution dissolves in excess sodium hydroxide. Magnesium doesn't dissolve in excess (2marks)

Can't remember any more questions so comment below if i missed anything or any corrections
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Lotus.An
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#2
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I think this year's paper is a little bit difficult.
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B0redBrioche
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#3
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#3
(Original post by Lotus.An)
Cool, can anyone recall the integration question with 5 and 1 as limitations?
Uhh I meant GCSE Chemistry C3 sorry lol
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Dreametuber
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#4
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#4
What did you get for the bond energy question at the end?... I got 81kj
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B0redBrioche
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#5
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(Original post by Dreametuber)
What did you get for the bond energy question at the end?... I got 81kj
I got -81 but i think either would be accepted
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Dreametuber
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#6
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#6
(Original post by B0redBrioche)
Didn't see one which had been made so I'll start

1)
a) Why does rainwater become hard?
The rainwater runs over rocks and calcium/magnesium ions dissolve into the water making it hard. (2marks)
b) Describe the graph include data
Solubility increases as temperature increases until it reaches 68 degrees (I think) and the solubility decreases as the temperature increases from 68 degrees onwards. Use data points. (3 marks)
c) Describe how ion exchange is used to soften hard water
Ion exchange columns contain hydrogen/sodium ions which displace the calcium ions in the hard water due to the sheer number of them and therefore the calcium ions are removed so the water is softened (3 marks?)
I think to get the mark for question 1 a i) you need to say acid rain
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haseebj49
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#7
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#7
Me too.


Posted from TSR Mobile
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headsway
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#8
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#8
(Original post by Dreametuber)
What did you get for the bond energy question at the end?... I got 81kj
i got -81 KJ
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SmokeNandos
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#9
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#9
Titration calculation one was 0.21mol/dm^3

one about sodium iodide or something it was yellow precipitate

6 marker was on calorimtery thingy measuring energy change so what i said was like record initial temp, mass of water, alcohol burner, then you light burner leave for 5 mins come back and blow it out and measure final temp, mass of what, alcohol burner and then u can calculate energy change

5 marker on titration

Measure acid use pipette to squeeze into flask
Put white tile under flask
add few drops of indicator in flask
Use pipette & squeeze the sodium hydroxide or w/e it was into burette and keep adding it until colour change/end point is reached

last question was bond making & bond breaking thingy

question about ticking boxes of energy change graphs etcc


question about rate of reaction calculation is 0.6

question on alumnium and idenitfying magnesium using excess sodium hydroxide

magnesium is present if solution dissolves in exccess sodium hydroxide




question about halide ions where everything was no change except for iron (II)) thingy which was green precipitate
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ASTROWRLD
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#10
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#10
(Original post by B0redBrioche)
Didn't see one which had been made so I'll start

1)
a) Why does rainwater become hard?
The rainwater runs over rocks and calcium/magnesium ions dissolve into the water making it hard. (2marks)

b) Describe the graph include data
Solubility increases as temperature increases until it reaches 68 degrees (I think) and the solubility decreases as the temperature increases from 68 degrees onwards. Use data points. (3 marks)

c) Describe how ion exchange is used to soften hard water
Ion exchange columns contain hydrogen/sodium ions which displace the calcium ions in the hard water due to the sheer number of them and therefore the calcium ions are removed so the water is softened (3 marks?)

2)
a+b) Tick boxes for overall energy change and formula of methanol (i think) (2 marks)

ci) 6 marker on calorimetry

cii) Make results more accurate
Use a lid or insulate the beaker so less energy is lost to the surroundings (2 marks)

3)
a) Why did M leave gaps?
For undiscovered elements (1 mark)

b) How were elements placed incorrectly?
Had different properties within groups, e.g. Chromium was in a group with 2 gases (1 mark)

c) Why is fluorine more reactive than iodine?
Less shells so Less shielding so stronger electrostatic forces and so more easily gained the final electron to become stable. (3 marks)

4)
a) 2 Changes between the reaction of water with potassium and lithium
Lithium is more reactive so more effervescence produced, more vigorous reaction and dissolves faster.
I thought potassium is more reactive?
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B0redBrioche
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#11
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#11
(Original post by WagwanPIFFTING)
I thought potassium is more reactive?
Yup of course sorry, I'll change it now
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elliebrown1203
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#12
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#12
What did people get for another reason, other than cost, why a lower pressure would be better? I said it was easier because less complex equipment is needed, do you think I would get the mark?
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Harrison.B 15
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#13
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#13
(Original post by Dreametuber)
I think to get the mark for question 1 a i) you need to say acid rain
No you don't.
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Harrison.B 15
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#14
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(Original post by elliebrown1203)
What did people get for another reason, other than cost, why a lower pressure would be better? I said it was easier because less complex equipment is needed, do you think I would get the mark?
I didn't know so I put it is less dangerous to have it at a lower pressure. I think you'll get the mark for that.
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elliebrown1203
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#15
(Original post by Harrison.B 15)
I didn't know so I put it is less dangerous to have it at a lower pressure. I think you'll get the mark for that.
I didn't even think of that thanks
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king_english
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#16
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#16
(Original post by elliebrown1203)
What did people get for another reason, other than cost, why a lower pressure would be better? I said it was easier because less complex equipment is needed, do you think I would get the mark?
correct

(Original post by B0redBrioche)
Didn't see one which had been made so I'll start

1)
a) Why does rainwater become hard?
The rainwater runs over rocks and calcium/magnesium ions dissolve into the water making it hard. (2marks)

b) Describe the graph include data
Solubility increases as temperature increases until it reaches 68 degrees (I think) and the solubility decreases as the temperature increases from 68 degrees onwards. Use data points. (3 marks)

c) Describe how ion exchange is used to soften hard water
Ion exchange columns contain hydrogen/sodium ions which displace the calcium ions in the hard water due to the sheer number of them and therefore the calcium ions are removed so the water is softened (3 marks?)

2)
a+b) Tick boxes for overall energy change and formula of methanol (i think) (2 marks)

ci) 6 marker on calorimetry

cii) Make results more accurate
Use a lid or insulate the beaker so less energy is lost to the surroundings (2 marks)

3)
a) Why did M leave gaps?
For undiscovered elements (1 mark)

b) How were elements placed incorrectly?
Had different properties within groups, e.g. Chromium was in a group with 2 gases (1 mark)

c) Why is fluorine more reactive than iodine?
Less shells so Less shielding so stronger electrostatic forces and so more easily gained the final electron to become stable. (3 marks)

4)
a) 2 Changes between the reaction of water with potassium and lithium
Potassium is more reactive so more effervescence produced, more vigorous reaction and dissolves faster. (2 marks)

b) Titration 5 marker
Measure acid use pipette to squeeze into flask
Put white tile under flask
add few drops of indicator in flask
Use pipette & squeeze the sodium hydroxide or w/e it was into burette and keep adding it until colour change/end point is reached
Swirl the flask while doing it

c) Calculate concentration- 0.21 (3 marks)

d) Precipitate questions
Iron II forms green precipitate
Iodide forms yellow precipitate

5a) Why moderately high temperature used?
Despite being exothermic in the forward direction they use a moderately high temperature to compromise between the yield and the rate of reaction. So high rate of reaction for a smaller yield produces more yield in the long term

b) Increasing the pressure
Increasing the pressure moves the reaction in the direction which produces less gas molecules which is the forward direction so more yield is produced

c) Why high pressure not used? (don't include cost)
Safety issues as it could damage infrastructure or a more complex infrastructure needed which wastes materials
Q3 b isnt right
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Harrison.B 15
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(Original post by elliebrown1203)
I didn't even think of that thanks
It was quite a hard paper so hopefully the grade boundaries will be low.
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Frankiitch
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#18
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#18
Another c3 mark scheme at https://www.thestudentroom.co.uk/sho....php?t=4781320
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B0redBrioche
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#19
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#19
(Original post by king_english)
correct



Q3 b isnt right
What's wrong about 3b)? I'll change it then
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Harrison.B 15
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#20
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#20
(Original post by king_english)
correct



Q3 b isnt right
What was the answer for 3b? I put that their electronic structures were different.
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