GCSE Chemistry Unit 2 and Unit 3 C2 C3 24th May 2012 Exam Discussion

Original post by steviep14

Ok I think in terms of C3 we need to know:

Flame Tests:
Lithium - Red
Sodium - Yellow
Barium - Apple Green
Potassium - Lilac
Calcium - Brick Red
Magnesium - No Change

Ion Tests:
Carbonate - Add Dilute HCl - Fizzing/Lime Water Milky
Halide - Nitric Acid + Silver Nitrate - Increasingly Yellow down the PT
Sulphate - Hydrochloric Acid + Barium Chloride - White ppt
Nitrate - Aluminium Powder + NaOH and Warm - Damp Red Litmus Paper goes Blue

Positive Ion Tests: (Add NaOH and Precipitate formed)
Copper - Blue
Iron 2 - Green turns Brown
Iron 3 - Reddy Brown
Aluminium - White and redissolves with excess NaOH
Magnesium - White ppt
Calcium - White ppt

You Also need only an Understanding of:
Atomic Absorption Spectroscopy - Identification of 40 elements in small amounts
Mass Spectrometry - Work out RAM of a Substance
IR Spectroscopy - Particular Bonds in a Molecule
NMR Spectroscopy - Structures of Organic Molecules
UV and Visible Light Spectroscopy - Amount of a substance in a solution

I just did this off the top of my head from revision so please correct me if I gave a wrong test result :wink:

But this is the list as far as I know

Flame test I also had copper - green! Hahaa apart from that, great revision :wink:

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Reply 22

Original post by _soph1

Flame test I also had copper - green! Hahaa apart from that, great revision :wink:

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Oh copper isn't in the revision guide or in the spec but it can do no harm learning it eh? :biggrin:

(Sneaks off to find the dreaded Specification :colone:

)

EDIT:
From C3 Specification: Flame tests can be used to identify metal ions. Lithium, sodium,
potassium, calcium and barium compounds produce distinctive
colours in flame tests.

(edited 11 years ago)

Reply 23

Original post by steviep14

Oh copper isn't in the revision guide :wink:

(Sneaks off to find the dreaded Specification :colone:

)

Hahaa ok I'll let you off then! Which rev guide have you got? That was just from the notes my teacher gave us :smile:

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Reply 24

AQA Science - GCSE Chemistry from Nelson Thornes
(Although I must say it isn't faultless :wink:

It is missing the Decomposition stuff so I'll go and read your post now :tongue:

)

Reply 25

Original post by steviep14

AQA Science - GCSE Chemistry from Nelson Thornes
(Although I must say it isn't faultless :wink:

It is missing the Decomposition stuff so I'll go and read your post now :tongue:

)

Ah, I have cgp and lonsdale. What decomposition stuff?!

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Reply 26

Original post by _soph1

Ah, I have cgp and lonsdale. What decomposition stuff?!

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From your post? :tongue:

Thermal Decomposition of Copper and Zinc Carbonate:
You put the carbonates over a bunsen flame...
Copper Carbonate (green) -------> Copper Oxide (black) + Carbon Dioxide
Zinc Carbonate (white) ----------> Zinc Oxide (yellow) + Carbon Dioxide

The Specification states you need to know these :redface:

Reply 27

Original post by steviep14

From your post? :tongue:

Thermal Decomposition of Copper and Zinc Carbonate:
You put the carbonates over a bunsen flame...
Copper Carbonate (green) -------> Copper Oxide (black) + Carbon Dioxide
Zinc Carbonate (white) ----------> Zinc Oxide (yellow) + Carbon Dioxide

The Specification states you need to know these :redface:

Ohh!

right well I'd better get revising :frown:

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Reply 28

I'm revising for this atm as well. I'm using the GCSE Chem AQA Nelson Thornes textbook and I was just wondering if anyone had the answers to the summary questions? (Stupid textbook doesn't have them). Also, what did you guys think of the B2 and B3 exams on Monday?

Reply 29

Original post by Unescaper

I'm revising for this atm as well. I'm using the GCSE Chem AQA Nelson Thornes textbook and I was just wondering if anyone had the answers to the summary questions? (Stupid textbook doesn't have them). Also, what did you guys think of the B2 and B3 exams on Monday?

I found them ok and I should hopefully find Chemistry ok too :biggrin:

and yourself?
Well if you post any questions you are unsure of here or PM me them I will take a look (I don't guarantee I will be right) but I am sure we can work out the answers together :tongue:

So feel free to PM me with questions if you like

Reply 30

Yeah, I thought they were okay. That question in B2 with the graph about Carbon taken in and given out confused me a bit. Ah well, hopefully I've done well.

Okay, so, here is the question:
If the percentage yield for a reaction is 100%, 60g of reactant A would make 80g of product C. How much of reactant A is needed to make 80g of product C if the percentage yield of the reaction is only 75%?

I got 87g but I'm not entirely sure.

Reply 31

Original post by Unescaper

Yeah, I thought they were okay. That question in B2 with the graph about Carbon taken in and given out confused me a bit. Ah well, hopefully I've done well.

Okay, so, here is the question:
If the percentage yield for a reaction is 100%, 60g of reactant A would make 80g of product C. How much of reactant A is needed to make 80g of product C if the percentage yield of the reaction is only 75%?

I got 87g but I'm not entirely sure.

Well 100% yield makes 1.33 Times A for C
so 0.33 x 0.75 = 0.2475
So 1.2475 time A for C
80/1.2475 = 64
64 x 1.2475 = ~80

100% Yield needs 60g of A to make 80g of C
75% Yield needs 64g of A to make 80g of C
I think :tongue:

Decreased yield means you need more reactants to make products but I am not sure I am right

Reply 32

AngryBirds4

Quick question -

The transition metals are really confusing me - I don't understand why they have incomplete lower energy-levels when I thought the maximum was 8, and why they have their own little section in the middle

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Reply 33

Original post by steviep14

Well 100% yield makes 1.33 Times A for C
so 0.33 x 0.75 = 0.2475
So 1.2475 time A for C
80/1.2475 = 64
64 x 1.2475 = ~80

100% Yield needs 60g of A to make 80g of C
75% Yield needs 64g of A to make 80g of C
I think :tongue:

Decreased yield means you need more reactants to make products but I am not sure I am right

Okay, that does sound right. I tried to do it by trial and error but I didn't actually work out what increasing the amount of A would do to C. Thanks!

Also, 0.333333... x 0.75 makes 0.25, so it does work.

(edited 11 years ago)

Reply 34

mjordanjnr

Is anyone elses C3 exam starting at 8.45 or is it only our school? :/

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Reply 35