Qualification > Sciences
IG Chemistry Paper 3 discussion
zara:
--- Quote from: Kim243 on June 03, 2009, 10:23:51 am ---Guys there are a few questions i wanted to make sure that they are correct
1-heat the solution--> i wrote to seperate crystals from water
2-what type of organic compound has the following linkage--->polyester
3-the complete question an alchohol group and an acid group (didnt write organic before acid:/)
4-advantages -->biodegradable so it wont cause pollution
5-water behaves as a base-->cuz its a proton acceptor
6- for the equation between sodium flouride and calcium chloride why was double the volume of NaF added?-->i wrote cuz 1 mole of CaCl2 reacts with 2 moles of NaF
7-condensation or addition? condensation cuz water was removed from the monomer
8-the stronger acid was HCl cuz it was 97% ionized
9-ph of HCl will be lower than the other acid (Or do i have to write values)?
10-for the raw materials i wrote -->fractional distillation of liquified air and cracking of an alkane (didnt notice that the process wasnt required)
11-the moles 0.07 same as silicon?and could somebody plz explain which one is limiting and why?
12-for the T formula i got the formula wrong but i wrote the volume of phosphate solution is double the volume of metal T nitrate solution for the explanation
13-for the exothermic reaction i got the values of reactants and products and checked which has greater value
I know the q's are too many but im kinda freaked out cuz i did very badly in the exam
--- End quote ---
1.to remove all the water
2.polyester
3.dont remember the ques
4.correct but they asked for two so u had to rite one more.
5.correct
6.dont remember if it came.
7.correct
8.dont remember the ques well..
9.even this one>>dont remember..
10.liquid air and methane
11.0.08>>same as silicon
12.i got this rong
13.dont remember the ques..
Kim243:
yay so the polyester one is right!!...but for silicon how come is it 0.08 i remember the ques was 0.07 moles of silicon reacted with 25 g of bromine O.o??maybe there were some differences in the exam...any more feedback?
zara:
well...different variant...well if silicon in ur ppr was 0.07 den the product will also be the same as dat of the limiting reagent.....n if in ur ppr it was COO...the linkage i mean well den its polytester...
Kim243:
yeah cuz some ppl kept sayin its ester or fats it didnt make any sense to me....anyone else? feedback?
....:
--- Quote from: robot_avenger on June 03, 2009, 10:33:27 am ---
--- Quote from: .... on June 02, 2009, 07:15:21 pm ---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 ...
PO43- + 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.
--- End quote ---
Dude I love You!!
I used exact same reasoning!!!!!
Atleast now i know i used valid reasoning!!
Thank you!
--- End quote ---
well..in my paper..i just wrote the formula, the first thing in my answer..then i made it clear the two volumes of the solution, then somehow i got a balanced symbol equation and wrote it down, and wrote after it..tht above is the chemical equation, according to the volume and mole ratios..hope thts an explanation that'll suffice
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