POLL: How did you do in your EDEXCEL A2 Chemistry Practicals: Watch

Poll: How did you do in the practicals?
Very Good (A) (52)
60.47%
Good (B) (15)
17.44%
Average (C or D) (8)
9.3%
Bad (E) (2)
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Fail (F) (9)
10.47%
"Hurricane"
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#41
Report Thread starter 12 years ago
#41
(Original post by theunforgiven)
hey i did the plan a bit differently. i said label the three solutions a,b and c and mix two at a time like a and b, b and c and a and c. the solution that has no ppte will have al and zn and the other solution will be nh3. is this okay?
Its true. Actually I thought of that at first, but then I decided to change. But problem will be that Zn will dissolve in NH3 in excess.
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Smashingdude
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#42
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#42
theunforgiven that is also a correct method. But u had NaOH with u so cud have probably done it the easier way. But ur method was flawless so u will get full marks for it. In MS they will mention different ways/plan to students attempts the questions. So u can go anyway round the plan but it shud be sensible/appropriate and can be done practically with the expected results.

pole substance C did smell like hell. Apart from that, i am sorry to say, iron doesnt give flame tests. It does give colored flames but it changes as it is a transition metal. So they are not characterstics for distinguish as it is for Na and K.
And u dont need a cobalt rod or something like that. u just use a wire, dipped in aq HCl and then rolled in the substance. Then subject it to BLUE bunsen flame(remeber not red. u have to set up the bunsen so it sparks up in blue).
It wud give u straight lilac colour.
Maybe u didnt heat the wire properly or didnt get enough of the substance on the platinum wire. Or u just tried it in brick red flame. Or there is another possibilty that the plaintum wire was dirty so it gave some other colour.
Also the platinum wire has its own charactersitic colour.
But be chill. u will loose only 2 marks if its wrong.
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"Hurricane"
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#43
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#43
(Original post by Smashingdude)
theunforgiven that is also a correct method. But u had NaOH with u so cud have probably done it the easier way. But ur method was flawless so u will get full marks for it. In MS they will mention different ways/plan to students attempts the questions. So u can go anyway round the plan but it shud be sensible/appropriate and can be done practically with the expected results.

pole substance C did smell like hell. Apart from that, i am sorry to say, iron doesnt give flame tests. It does give colored flames but it changes as it is a transition metal. So they are not characterstics for distinguish as it is for Na and K.
And u dont need a cobalt rod or something like that. u just use a wire, dipped in aq HCl and then rolled in the substance. Then subject it to BLUE bunsen flame(remeber not red. u have to set up the bunsen so it sparks up in blue).
It wud give u straight lilac colour.
Maybe u didnt heat the wire properly or didnt get enough of the substance on the platinum wire. Or u just tried it in brick red flame. Or there is another possibilty that the plaintum wire was dirty so it gave some other colour.
Also the platinum wire has its own charactersitic colour.
But be chill. u will loose only 2 marks if its wrong.
What about you SmashingDude, what did you write in your plan? That's if you want to share it ofcourse
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medic88
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#44
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#44
Hi every1 thanx for all the help!

Just wanted to ask:
1. which separation method should be used simple filteration, filteration unde reduced pressure (Buchner) or decanting
2.do you have to add HCl to free the cations at the end?

Thanks - any help appreciated
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"Hurricane"
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#45
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#45
(Original post by medic88)
Hi every1 thanx for all the help!

Just wanted to ask:
1. which separation method should be used simple filteration, filteration unde reduced pressure (Buchner) or decanting
2.do you have to add HCl to free the cations at the end?

Thanks - any help appreciated
1.Simple filteration is enough.
2.Zn is already a cation.
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Smashingdude
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#46
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#46
Abburuman i wrote the plan which i said previously expect i used NaOH to distinguish between them first.
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medic88
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#47
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#47
(Original post by Aburumman)
1.Simple filteration is enough.
2.Zn is already a cation.
Thanx
for part 2. i meant abot the Al 3+ (as it has formed a ppt)
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ajcool
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#48
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#48
guys you know for ques 2b- what isomers did you draw?
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Jean
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#49
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#49
primary alcohol and secondary alcohol..
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"Hurricane"
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#50
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#50
(Original post by medic88)
Thanx
for part 2. i meant abot the Al 3+ (as it has formed a ppt)
They didnt ask for the Al. They only wanted us to obtain Zn in the form of a cation, that is the filterate.
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"Hurricane"
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#51
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#51
(Original post by Smashingdude)
Abburuman i wrote the plan which i said previously expect i used NaOH to distinguish between them first.
So you did like I did. My plan is on the first page.
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Mustard-man
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#52
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#52
(Original post by Jean)
primary alcohol and secondary alcohol..
what was the answer for distinguishing them? This was the only question I didn't know :confused:
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Jean
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#53
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#53
you can do the idoform test. the reagents are given in the user guide. secondary alcohol will give positive result as it has the -RCH(OH)CH3. primary will give you nothing.
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kingalan
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#54
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#54
(Original post by Mustard-man)
what was the answer for distinguishing them? This was the only question I didn't know :confused:

you oxidise the alcohols with acidified potassium dichromate...then add 2,4-DNP..then do silver mirror test....this is a correct way.......but they only gave us one line....i thought it musta bin sumthin short...and i ran outta time to write it...
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genie k
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#55
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#55
(Original post by shimmerinapple)
I got the Fehling's solution wrong, it didnt change coloud, so i thought it was a ketone..so my questions for all the following questions are all wrong.

HEY SHIMMERINAPPLE I DONE THE SAME THING!!! AHHH I CNT BELIVE IT.
IT WAS BLUE WHEN I 1ST SAW IT SO I THOUGHT YEA ITS A KETONE. THEN AFTER THE END OF THE EXAM. THE TEACHER TOLD US 2 EMPTY THE SOLOUTIONS OUT. AND WHEN I WAS EMPTYING IT I SAW A RED PTT AT THE BOTTOM! N I WAS LIKE OHHH CRAPPPPPPP. N I COULDNT CHNAGE THE ANSWA AS THEY TOOK THE PAPER IN:mad:
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Jean
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#56
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#56
(Original post by kingalan)
you oxidise the alcohols with acidified potassium dichromate...then add 2,4-DNP..then do silver mirror test....this is a correct way.......but they only gave us one line....i thought it musta bin sumthin short...and i ran outta time to write it...
:eek: So long??! Iodoform test is enough. Trust me.
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kingalan
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#57
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#57
yeh i jus didnt think...i had like 5 minutes left...but the rest of the paper was wikkid...
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Jean
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#58
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#58
The Fehling stuff is really bad. The colour was so dark, hardly see the red ppte at all. I only saw a faint red ring on top.
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Jean
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#59
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#59
(Original post by kingalan)
yeh i jus didnt think...i had like 5 minutes left...but the rest of the paper was wikkid...
I had 20 mins left after all the answering.
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Prometheus
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#60
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#60
Part B: Seperate between a mixture of ZnCl2 and AlCl3, you should get Zn2+ ions => Use simple distillation, Zn2+ as filterate.
How can you distil ions?

Wouldnt you just add excess NH3, filter off the Zn2+/Cl- ions and your left with the Al ppt?
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