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Author Topic: IG Chemistry Paper 3 discussion  (Read 24318 times)

Offline sweetie

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Re: IG Chemistry Paper 3 discussion
« Reply #165 on: June 02, 2009, 04:15:44 pm »
Quote from: bibo the wa7sh on June 02, 2009, 04:03:35 pm
heY everYone,
wat about electrolysis of dilute sodium chloride???
Cathode..........
anode..............
and wat happens to the electrolyte???.....
WaiTinG 4 uR RepLies!!xD!!
at da cathode it was h2
at anode it was o2
so conc. NaCl was left
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Offline Shogun

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Re: IG Chemistry Paper 3 discussion
« Reply #166 on: June 02, 2009, 04:17:05 pm »
By the way to make an ester, u must write
carboxylic/ carboxylic gourp / or at least COOH    AND hydroxyl/hydorxyl group/alcohols or atleast Oh

^and waht notty_me said about the elctrolysis stuff is correct..
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Offline sweetie

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Re: IG Chemistry Paper 3 discussion
« Reply #167 on: June 02, 2009, 04:17:28 pm »
i got this tooooooo
but how do we no wats da valency of T?????????/
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Offline hdbkiwi

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Re: IG Chemistry Paper 3 discussion
« Reply #168 on: June 02, 2009, 04:19:14 pm »
Quote from: horror on June 02, 2009, 04:13:03 pm
Quote from: bibo the wa7sh on June 02, 2009, 04:03:35 pm
heY everYone,
wat about electrolysis of dilute sodium chloride???
Cathode..........
anode..............
and wat happens to the electrolyte???.....
WaiTinG 4 uR RepLies!!xD!!
Cathode:sodium
anode chloride
electrolyte: used up
+rep me

nonono-the dilute sodium chloride means that you have more H+ and OH- in solution than Na+ and Cl-
soo
at the cathode, reduction occurs-in this DILUTE solution, hydrogen gas forms (half equation: 4H+(aq) + 4e-->2H2(g)
at the anode, OH- ions give up electrons, since not many Cl- ions are present. Oxygen bubbles off: 4OH- -->O2(g) +2H2O(l) +4e
When the hydrogen and oxygen bubble off, the Na+ and Cl- ions are left behind-so we still have a solution of sodium chloride!
The overall result is that water has been decomposed.

And for the Haber process question:
Air is nearly 80% nitrogen and 20% oxygen, with just small amounts of other gases. The oxygen is removed by burning hydrogen in the air.
2H2(g) + O2(g) -->2H2O (l)
That leaves mainly nitrogen.

Or you can say "the fractional distillation of liquid air"-another way to obtain nitrogen.

For Hydrogen:It is usually made from natural gas or methane, and water (as steam):
CH4(g) + 2H2O (g) -->(catalyst) CO2 (g) +4H2(g)
or you can crack compounds in oil (the alkanes)
« Last Edit: June 02, 2009, 04:23:54 pm by hdbkiwi »
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Offline Shogun

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Re: IG Chemistry Paper 3 discussion
« Reply #169 on: June 02, 2009, 04:21:31 pm »
see on the anode is oxygen on the (u cannot expect water to be stucked at the anode u know)
then hydrogen on the cathode as it is dilute and aqueous leveng chlorine and sodium, giving sodium chloride.
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Offline sweetie

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Re: IG Chemistry Paper 3 discussion
« Reply #170 on: June 02, 2009, 04:45:19 pm »
Quote from: Shogun on June 02, 2009, 04:17:05 pm
By the way to make an ester, u must write
carboxylic/ carboxylic gourp / or at least COOH    AND hydroxyl/hydorxyl group/alcohols or atleast Oh


isnt it dicarboxylic or diol?????
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Offline sweetie

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Re: IG Chemistry Paper 3 discussion
« Reply #171 on: June 02, 2009, 04:46:18 pm »
Quote from: notty_me on June 02, 2009, 04:17:28 pm
i got this tooooooo
but how do we no wats da valency of T?????????/

plzzzzzzzzzz i need a reply

thanx
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Offline Kim

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Re: IG Chemistry Paper 3 discussion
« Reply #172 on: June 02, 2009, 04:47:56 pm »
i wrote t3(po4)2
meaning my T valency was 2 because in the graph the height of the precipitate was twice the height of the volume so i wrote 2 many in my skul did dat
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Offline Shogun

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Re: IG Chemistry Paper 3 discussion
« Reply #173 on: June 02, 2009, 04:49:01 pm »
thts for u to guess, we dont know.

this is what the question ask, the question in short says what is the valency of metal T, and u will only get the formula if u know the valency of T, but to get it, its for u to find out...

i got mine as 1 others got 2...
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Offline hdbkiwi

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Re: IG Chemistry Paper 3 discussion
« Reply #174 on: June 02, 2009, 04:49:22 pm »
Quote from: kim on June 02, 2009, 04:47:56 pm
i wrote t3(po4)2
meaning my T valency was 2 because in the graph the height of the precipitate was twice the height of the volume so i wrote 2 many in my skul did dat


yeeees-I got the same as you!: )
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Offline ETCH

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Re: IG Chemistry Paper 3 discussion
« Reply #175 on: June 02, 2009, 04:58:10 pm »
i got 1 since they gave us conc. and volume so i calculated no. of moles and wrote a balanced ionic equation it was somethin like this 18T+6P04=6T3p04
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Offline killzone

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Re: IG Chemistry Paper 3 discussion
« Reply #176 on: June 02, 2009, 05:28:37 pm »
Quote from: mr3bood on June 01, 2009, 10:30:22 pm
what about the chlorophyll question?....the first one where it says *how can you show that this green solution contains chlorophyll*?...and the second one that has 3 marks!...*expain the role of chlorophyll*?...

1) i think u should put the pure sample of chlorophyll in the pencil line a long with a sample from the green solution ,, the pure sample cuz its pure is gonna give one spot on the paper, but the green solution is gonna give many so if there a spot that matches the spot of the pure sample that means that it actually contains chlorophyll.

2) chlorophyll traps sunlight need for the process
   it also acts as the catalyst for the reaction
   it also gives the plant its green color
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Offline horror

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Re: IG Chemistry Paper 3 discussion
« Reply #177 on: June 02, 2009, 05:31:08 pm »
Quote from: Shogun on June 02, 2009, 04:14:51 pm
Quote from: horror on June 02, 2009, 04:10:44 pm
Quote from: horror on June 02, 2009, 04:08:49 pm
Quote from: notty_me on June 02, 2009, 04:01:47 pm
hiiiiiiiiii every1
shogun can u tell me the formula u got 4 da phosphate?

all da best 4 da rest of ur xams     










Its K2PO4 :)


lol i got P3PO4 it cant be p2 cuz the valency of p4 is 3
I've discussed the question with my teacher and she said that its K2PO4 ....potassium displaces sodium from it salt because potassium is more reactive than sodium. :D
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Offline Shogun

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Re: IG Chemistry Paper 3 discussion
« Reply #178 on: June 02, 2009, 05:35:53 pm »
even i thought its potassium.. but isnt the valency of the radicle phosphate is 3....
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Offline hdbkiwi

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Re: IG Chemistry Paper 3 discussion
« Reply #179 on: June 02, 2009, 05:55:36 pm »
Quote from: horror on June 02, 2009, 05:31:08 pm
Quote from: Shogun on June 02, 2009, 04:14:51 pm
Quote from: horror on June 02, 2009, 04:10:44 pm
Quote from: horror on June 02, 2009, 04:08:49 pm
Quote from: notty_me on June 02, 2009, 04:01:47 pm
hiiiiiiiiii every1
shogun can u tell me the formula u got 4 da phosphate?

all da best 4 da rest of ur xams     










Its K2PO4 :)


lol i got P3PO4 it cant be p2 cuz the valency of p4 is 3
I've discussed the question with my teacher and she said that its K2PO4 ....potassium displaces sodium from it salt because potassium is more reactive than sodium. :D

It can't be K2PO4

PO4 is 3-
K is +1

phosphates form with ferrous metals, the most likely candidates being iron or nickel
it was a 2+ metal as the precipitate height was twice that of the volume used (although thinking back now did the concentration work out to 1 mole??? urgh)
^^
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