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Unofficial AQA Chemistry Unit 3 GCSE NEW SPEC Higher Tier Mark Scheme

Mark scheme being created!
Help with the mark scheme would be greatly appreciated, also it would be great if someone could write the number of marks and the order of the questions for the one's I don't know

Question 1
a)What gas is given off?
Hydrogen (1 Mark)
b)What ion causes this solution to be alkaline?
Hydroxide Ions (OH−) (1 Mark)
c) Give two differences between Potassium & Lithium when reacted with water
List any of the following two:
- Potassium is more reactive therefore there will be a much more vigorous reaction
- With Potassium the hydrogen can ignite
- Potassium there is more movement on the surface of the water
(2 Marks)

Question 2
a)Draw the rest of the structural formula.
b)The alcohol reacts with oxygen/microbes/oxidizing agents
and the reaction is oxidation/exothermic
(2 Marks)
c)Circle

Question 3
Titration Experiment
Put acid in the burette
• pipette used for alkali to put into burette
• read meniscus at eye level
• acid added dropwise (open the tap)
• indicator used (for example methyl orange)
• white background / tile
• end-point of titration recorded
• swirling / mixing
• repeat
(6 Marks)

Question 4
a)Calculate the mean:
11 + 13 = 24/2 = 12 drops (Ignore anomalous result)
(2 Marks)
b)What do the results show about the different water samples?
-Spring water is the hardest
-Tap water softer than spring water, harder than distilled water
-Distilled water softest/soft water
(3 Marks)
c)Why is there a white solid in the pan?
-Hydrogen carbonate ions decompose
-Form carbonate ions
-Reacted with calcium and magnesium ions to form an insoluble precipitate
-This is limescale/ the white solid.
(3 Marks)

Question 5
a)How do you test for potassium and sodium?
-Flame Test
-Sodium - yellow flame
-Potassium - lilac flame
(3 Marks)
b)Why could the potassium not be identified?
-The yellow sodium flame masks the lilac potassium flame (1 Mark)
c)How do you prove it is Mg or Ca rather than Al? (2 Marks)
-Add excess sodium hydroxide
-If Al present than precipitate dissolves if not then must be Ca or Mg
(2 Marks)
d)How can you tell they are not Ca ions?
-Flame test
-If not red under flame test then not Calcium
(2 Marks)

Haber Process Questions (Wrong Order Sorry)
1.Where does the nitrogen in the Haber process come from
-The air
(1 Mark)
2. Why is the temperature at 450 in the Haber process
-Compromise
-Between a good yield
-And a appropriate temperature.
(3 Marks)
3. What is part x for?
-Transports excess nitrogen and hydrogen
-Which can be used to produce more ammonia
(2 Marks Unsure of this)

Questions Is Any Order Unsure Of Question Number:
1.State One Advantage And One Disadvantage of adding Chlorine to water:
Advantage:
-Kills bacteria
Disadvantage:
-Increased likely hood of cancer
(2 Marks)
2.The energy transfer calculation
- 4.2 x 750g x 47 = 148050J
(3 Marks)

My Predicted Grade Boundaries (Based upon this poll):
A* - 51
A - 41
B - 34
C - 26
D - 19

(edited 10 years ago)

Scroll to see replies

Reply 1

rihannagirl

wooooooooooooooooooooooooo

Reply 2

naomi.x

so where is the mark scheme???

Reply 3

HennersPD

For question 7 (about bond energies) I got the overall energy released as -2049 kJ and for the first QU. It was about OH- ions and an oxidation reaction! :smile:

http://poll.pollcode.com/llsdc Go here to vote for the difficulty of the exam so we can get grade boundary estimates!

Reply 6

robster01

Change it to Unofficial, we're not AQA!

Q5
a) How do you test for potassium and sodium? (3)
-flame test (1)
-Potassium - lilac (1)
-Sodium - yellow (1)
(maybe add cleaning the ring)
b) Why could the potassium not be identified?
-The yellow sodium flame masks the lilac potassium flame
c) How do you prove it is Mg+ or Ca2+ rather than Al+? (2 I think)
-excess sodium hydroxide (1)
-Al+ precipitate re-dissolve (1)
d) How can you tell they are not Ca2+ ions?
-flame test (1)
-NOT red, NOT Calcium (1)

I think, may be some errors in there

Reply 7

Sean Robinson

How much marks do you reckon would equate to 74 UMS? just an estimate anything! need to know if it's worth revising for my C1 retake, or concentrating on other subjects

Reply 8

SportsFan

Original post by robster01

Change it to Unofficial, we're not AQA!

Need a moderator to change it for me

Reply 9

shibucool

2d or 2cii I think it was ester then propanol

Reply 10

matthealey

Original post by Sean Robinson

How much marks do you reckon would equate to 74 UMS? just an estimate anything! need to know if it's worth revising for my C1 retake, or concentrating on other subjects

i'm guessing about 55%, based on last years c2 anyway not sure though

Reply 11

user4600

Original post by Kill3er

Dammit I only circled the C(double bond) O arghhhhh

Posted from TSR Mobile

Reply 12

matthealey

for the average question, do you need to discard the anomalous result (6) or just calculate the mean of all three?

Reply 13

redz0r

I think the first question is oxygen and -OH ions. Even though I did put hydrogen

Reply 14

matthealey

Original post by redz0r

I think the first question is oxygen and -OH ions. Even though I did put hydrogen

its definitely hydrogen

Reply 15

holly12345

Is the water one questions 4?
If it is
1) 11 + 13 = 24/2 = 12 drops (Ignore anomalous result)
2) What do the results show about the different water samples? (Can't remember what I put)
3) Why is there a white solid in the pan?
- Temporary hard water. Boiled - hydrogencarbonate ions decomposed to form carbonate ions which reacted with calcium and magnesium ions to form an insoluble precipitate of magnesium carbonate or calcium carbonate. This is limescale/ the white solid.

Not too sure if it's right?

Reply 16

seawhim

You probably shouldn't base grade boundaries completely on the poll--it's pretty likely that those of us who are making an active effort to see what we got in the exam are more higher grading than average students. There has to be some connection, anyway. The majority of "normal" people who I asked thought the exam was difficult.

Reply 17

robster01

Original post by matthealey

for the average question, do you need to discard the anomalous result (6) or just calculate the mean of all three?

I removed it, there was one like that in B2 last time :P

Main calculations

Q = mct
Q = 750*4.2*(64-17)
Q = 148050J

Moles = 6/ 44 = 0.1363636... moles
148050/ 0.136363636... = 1085700J
1085700/ 1000 = 1085.7kJ

3(2(803)) + 4(2(CANT REMEMBER NUMBER)) = 85??

64?? - ^^ = -2049

(edited 10 years ago)

Reply 18

alecbritton