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Makematics

hwpo13
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yeah me too... didn't even see it as oxidation/reduction, i just said they both needed one electron for full shell therefore not sponaneous...
Lel better than me, i used the cell potentials table and somehow incorrectly found it to be spontaneous
 

superSAIyan2

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only 2. you could also explain it by saying bromine has a greater tendency to oxidise in the presence of chlorine and hence will not reduce.
 

RealiseNothing

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In the reaction chloride ions are oxidised to chlorine gas and bromine liquids is reduced to bromide ions.
Anode: 2Cl(-) ----> Cl2 + 2e- E(oxidation) = -1.36V
Cathode: Br2 + 2e- ----> Br- E(reduction) = 1.08V
cell potential is -0.28V <0 therefore nonspontanteous
I had exactly this yay.
 

KoshX87

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For the 2nd short answer page did you guys get:
a) Lead Sulphate (I wasn't too sure)
b) Ba2+ + 2Cl- --> BaCl2 (with states as aqueous)
c) I wrote that you would use a platinum rod and dip it into the solution. A green flame test would indicate copper. Anyone?
 

superSAIyan2

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i got
a) Barium Shulfate
b) Pb2+ + 2Cl- = PbCl2
c) Add sodium hydroxide. Formation of blue precipitate suggests copper ions are present. To confirm dissolve precipitate in excess ammonia; a deep blue complex forms if copper is present.

KoshX87 How did u get a precipitate in aqueous state?
 

hayabusaboston

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OK Im trying to recall all the mistakes I remember i did in the test, ive got so far:
-2 for MC
-1 or -2 for lead and silver nitrate q
-1 for spontaneous reaction q
-1 for equilibrium constant q
Possibly -2 for industrial 7 marker
-1 for one of the validity q's
-1 for another q I forgot


Can someone plz just list the harder q's, I forgot some of them, trying to remember my errors.
 

KoshX87

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i got
a) Barium Shulfate
b) Pb2+ + 2Cl- = PbCl2
c) Add sodium hydroxide. Formation of blue precipitate suggests copper ions are present. To confirm dissolve precipitate in excess ammonia; a deep blue complex forms if copper is present.

KoshX87 How did u get a precipitate in aqueous state?
I went to the toilet and realised that, but i need to study for physics so i did a bit and didn't bother changing lol
 

KoshX87

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And yes i realise i screwed that question. I might still get marks for the Copper part though
 

Queenroot

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i got
a) Barium Shulfate
b) Pb2+ + 2Cl- = PbCl2
c) Add sodium hydroxide. Formation of blue precipitate suggests copper ions are present. To confirm dissolve precipitate in excess ammonia; a deep blue complex forms if copper is present.
KoshX87 How did u get a precipitate in aqueous state?
I said sodium carbonate and a light blue precipitate would form and left it at that... Lol
 

hayabusaboston

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lol I what I've heard of students getting raw marks of high 80s last year and that's still a state rank
U joking arent u? lol I will probs as the days go by find more errors I did anyway...

Fuck it, cant change what happened, focus on getting a band 6 in physics now.
 

bangladesh

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I said sodium carbonate and a light blue precipitate would form and left it at that... Lol
It's sodium hydroxide. But yeah i said blue ppt. I think that should be enough for 2 marks.

So far I've lost like 5 marks.
 

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