IG Chemistry Paper 3 discussion

[....]

what i think was that the value of the height had nothing to do with the volume, since height was in mm, and volume in cm³. I just remember that, 18 cm³ of aqueous nitrate of T, reacted with 2 cm³ portions of a solution of Na₃PO₄. The maximum precipitate of the phosphate of T, was reached at 6 cm³ of sodium phosphate. Since both had the same concentration, it didnt really matter, the main thing that mattered was the volume then. Now, we have that the volume of the nitrate of T used was 18, and that of the sodium phosphate was 6. so volume ratio of the nitrate reactant to the phosphate reactant is 18:6 = 3:1, which is also the mole ratio. So if we construct an ionic equation using the mole ratio, we can get ...

PO₄^3-  +  3T⁺  ---->  T₃PO₄

when i came home, i opened june 2004 paper 3, of chem, where i remember seeing a similar graph as the one given in the question..

in the june 2004 q, 4 cm³ of aqueous iron (III) chloride, reacts with 2cm^3 portions of aqueous sodium hydroxide..according to the graph..the maximum volume of sodium hydroxide at which the maximum precipitate is formed, is at 12 cm^3..

thus the volume ratio of the chloride reactant to the hydroxide, is 4:12 = 1:3
That means, there will be one Fe³⁺ ion for every 3 OH^- ions..according to the ratio..

the next part of the given is..complete the following reaction..

Fe³⁺   +   .....OH^-  -----> ...........

since ratio is 1:3..itll be 3 OH^- forms Fe(OH)₂..
the concentration of both reactants is 1moldm^-3 which is given..

so the questions are quite similar..and so, i think T₃PO₄

i dont consider myself a genius, just mixxing familiar stuff with unfamiliar stuff.

[....]

sorry...that is Fe(OH)₃

[Shogun]

it wasnt OH in tht fe thing it was some halogen i think, im100% sure it wasnt OH in the fill in the blanks stuff for tht ionic reaction. however ure explaination is good.

[....]

i just rechecked it..and it is aqueous sodium hydroxide, and aqueous iron (III) chloride..as the reactants..:S

[shafiq_92libra]

At da cathod(da negativ electrod) u gt H2+ ions atraced n dey giv H2 gas at cathod. At da anode wich is positiv, da negtiv ions dat r Cl- ions r atracted n dey giv off Cl2 gas. A solution of NaOH is left behind

[MaNa]

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

NOPE its was concentrated NaCl
therefore @ anode Cl would be depsoed no O2

[IO4567]

no... im pretty sure it said dilute sodium chloride

[esso]

properties of Cao
did it come....cause i think there is diffrent papers

[~M.J~]

Guyz...
a bad news
test 4 carboxylic acis is not litmus ppr
the question was to give a test to show that it contains -COOH ions
i searched the net
googled "test 4 carboxylic acid Chemistry" n got the ans.

Test: add water then add sodium hydrogen carbonate
Result: Fizzing and a white ppt. at the bottom

This test is specifically for carboxylic acids and i think they asked this one
not the little litmus paper.......

[....]

properties of CaO came in the way, that the ionic structure we had to draw was originally calcium oxide, so we had to tell its properties..

and, about organic acids..i think syllabus specifies that we have to know about ehtanoic acid as a typical weak acid..and so..TYPICAL weak ACID, means, that it reacts in the same way with litmus, metal carbonates, hydroxides, oxides, and even metal themselves as mineral acids..well..when we have to test for an acid, we guys used to use the carbonate test, effervescence occurs, and the gas produced turns limewater milky...what about the rest of you??

[~M.J~]

I just can't  understand why the CIE nutshells wrote "to show the -COOH"
y not just "to show that they r week acids"

[....]

lol..maybe thts a way to make sure the candidate even knows that -COOH is for a carboxylic acid..
well..what did you write for this acid test?

[thukon]

For the COOH thingy, i wrote add and alcohol and an ester should form Its a long shot i know, but at least its a test to show that they have the COOH group and not just to show that they are acids.

[aquarian93]

which question was "to show a test to distinguish b/w the two?"
one had a double bond so i did add Bromine, and it would decoulirise unlike the other, forgot which question it was.


and guys, how much is the boundary for an A? does anyone noe?

[thukon]

which question was "to show a test to distinguish b/w the two?"
one had a double bond so i did add Bromine, and it would decoulirise unlike the other, forgot which question it was.


and guys, how much is the boundary for an A? does anyone noe?

I wrote the same thing. Shake with bromine water.