tomorrow is the edexcel A2 practical Watch

nighty
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any help plz ? what to take ? what questions coming? i need help plz
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Kieny
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(Original post by nighty)
any help plz ? what to take ? what questions coming? i need help plz
HI there!

U know the basic layout right...

1. Identify 2 compounds (inorganic)
2. Identify 2 organic
3. Boiling point (measure)
4. Plan a series of tests to identify 3 compounds and plan simple procedure to separate the cations



Well....

1. Fairly easy just use your guide - standard tests and stuff
2. Ditto
3. A bit tricky to nail the bpt - but ... whatever
4. Planning


With Planning i've got some inside info...
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Hoggers
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hey. some inside info? any chance of sharing that with us? ive heard the three cations will be Al, Zn, and Mg, Is that true? :confused:
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Kieny
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Mmmm...

Al and Mg im not sure but i think Zn is a safe bet!
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nighty
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can u help a bit more plz?
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Kieny
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(Original post by nighty)
can u help a bit more plz?
Ok ...

Basically for the planning they will either give NaOH or NH3. I think wht they wud as the first part wud be to identify each.(like they did in AS). So this is easy. Add NaOH or NH3 and observe the ppt. Compare with table. If necessary add excess to see if dissolves(i seriously dont remeber anyone of the tests now but i will go thru these in an hour and then post the Whole proposed plan)

The second i think they wud say 2 of the solutions are now mixed. Plan how wud u separte those. Now i am confused here. That means we have to write plan for all possible combinations (Al,Zn or Zn,Mg or Al,Mg) So in each case we ppt it out using NaOH/NH3. One will dissolve and the other wont in excess.

After this its all separation filteration/Recrystallization as necessary ...


Hope this helps a bit

Good Luck!!!##

P.S - I hear Fe 3+ will come up in the inorganic analysis...
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nighty
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thanks man waiting more when u finish the plan can u put it here plz? can u give me a discribtion how will the exam be ? like first question etc
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Kieny
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(Original post by nighty)
thanks man waiting more when u finish the plan can u put it here plz? can u give me a discribtion how will the exam be ? like first question etc
I think u should check out the 6a of the specimen edexcel paper - just scroll down to paper 6a (p.79)...

http://www.edexcel.org.uk/VirtualContent/25063.pdf

U've got the mark scheme there 2 .. so u can check where you're not geoing right.

Good Luck
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nighty
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hey there can u tell me what will the plan be and the procedure plz?
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Kieny
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(Original post by nighty)
hey there can u tell me what will the plan be and the procedure plz?
Hi!

'You are required to plan a series of tests to identify three compounds and to plan a simple procedure to separate the cations in two of the compounds'

I hear that the 3 compounds are gonna be Al, Mg and Zn salts. With regard to the procedure - im onto it .. but this is what ive got so far...

Part (a):

Label the solutions as A,B,C
Take about 5cm(cube) of A and pour it into a Test tube
Add 2cm(cube) of NaOH
A ppt forms.
Add excess NaOH and see if the precipitate dissolves
Carry out the test with the other 2 solutions.

Inferences:
If a white ppt forms and it doesnt dissolves in excess, then Mg ions are present in the original solution. Label the solution as MgCl
If a white ppt forms and it dissolves in excess, then either Al or Zn ions are present.

Now take 5cm(cube) of one of the other 2 solutions and pour it into a testube
Add 2cm(cube) of NH3
A ppt forms
Add excess and see if the precipitate dissolves.
Carry out the test with the other solution.

Inferences:
If a whit ppt whit is insoluble in excess reagent forms, then Alumunium ions are originally present. Mark the solution as Aluminum Sulphate
If a white ppt which is soluble in excess reagent, then Zinc ions are present. Mark the other solution as Zinc Sulphate


As you may have realised this doesnt address the issue of separating the cations only identifying them - i havent got round to that yet. I cant really predict it because i dont know what they will ask is mixed!!

I hope u find this useful - and i hope i'm right and this is correct!

Good Luck again

I hope i have been of help...
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Aelk_47
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to separate the cations i fink u hav to filter the ppt thn it leaves u wiv the residue which should contain the cation. im not sure but thts wot i hav heard somethin along the lines of filterin
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digimatrix
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WOw this is really good info. I only had an idea that transition metals might come but your plan was really helpful. Thanks, KIENY!
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