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IG Chemistry Paper 3 discussion
XaM!!:
As far as i remembrd dat Aluminium n Carbn compound ws Aluminium Carbonate... Dat T formula i wrote T3(PO4)2... N in dat exo ques i did sum calculatns dan wrote It is an exo because change in temp is in negative n Energy required for bond breakng is less dan energy releasd during bond formation... Limitng reactant ws Si n moles vr 0.08... Abt role of chlorophyl i wrote de trap lyt to cary photosynthesis n de gve colour 2 da plant... N abt PLV advantages i wrote it is cheap as it can be made frm a corn compard 2 petrol n secnd one ws it s biodegrable... Dat circled portion ws Ester group... N it was condensation polymer BECOZ IT CONTAIND DOUBLE BOND...! Mmmm dan dan dan... Ya dat raw material 4 ammonia i wrote Liquid air n 4 hydrogen i wrote Methane(water s also corect).. Use i wrote Fertilizers... Iron ws da catalyst... There ws a ques abt HCl n HF... I wrote HCl ws strong acid n Hf weak... Hope ths is corect... N dat metal ques, electrolysis... I forgot dm... Plz corect me if i gave any wrng ans...
qwert101:
--- Quote from: horror on June 02, 2009, 08:36:43 am ---
--- Quote from: qwert101 on June 02, 2009, 06:51:07 am ---
--- Quote from: sweetest angel on June 02, 2009, 06:49:06 am ---
--- Quote from: horror on June 02, 2009, 03:18:22 am ---
--- Quote from: Wahab09 on June 02, 2009, 12:42:34 am ---"for the indicator question..i wrote pH meter........i know it's wrong..but at least i wrote something...who knows..i might get it right anyway.......and for the Aluminium question i didnt balance it...so i think i got 1 for a non balanced equation instead of 2..."
dude.. dip a pH meter is 100% correct..!
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Its 100% wrong PH meter is an indicator .they said how would you test if the 2 something is acidic without an indicator ....test: add any metal sodium for example ...results: hydrogen gas revolves....-rep me if am wrong and +rep me if am right :D
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I ADDED A CARBONATE: GAS GIVEN OFF WHEN PASSED THROUGH LIME WATER TURNS IT MILKY...EH?
AND FOR THE BOND ENERGY ITS PRODUCT ENERGY _ REACTANT ENERGIES NT DA OPPOSITE
THUS POSITIVE ANSWER 'N RXN IS EXOTHERMIC!!
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negative answer is exothermic and I also said carbonate- if u said metal or metal oxide it would also react with water hence not correct ;)
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The exact question if am not mistaken is "describe a test other than the use of indicator to show that both chemicals belongs to an acidic group <----I don't see no water in the question so the test is by reacting a metal and the result is hydrogen gas revolves am sure of the answer i've discussed the queston with my chemistry teach am definately right :)
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if many things react with it, its not much of a test is it? Either way, if your right, both answers are correct ;)
Shogun:
hey i thought i can say the ans now,
1)was u had to draw chramatography.
2)explain how u see the cholorophyl in the chramotogram and compare with known spots of chlorophyl, or check and compare Rf value.
3)- write about photosynthesis
- write what does it do (i.e help to trapl sunlight for enegy to combine carbondiaoxide and water)
- write the products of photosynthesis (i.e oxygen and glucose)
then comes tht stuff for elctrolysis.
where an OH is relesed write on the anode the sunstance oxygen (there will be 2 answers with oxygen on the change of anode in this question)
then there was hydrogen and i think copper for change in cathode.
and the last one was aqueous concentrated pottasium bromide.
then i think came the question of periodic table stuff which is easy... i dont think i have to discuss it.
then cam the question of unfamiliar and familiar metals, now this is the only part in the exam i had trouble with. the first 2 question of it i messed up i think (well maybe the frist only the most). the ans for barium was +2, and the answer for the last one i wroet "cuz the same metal is able to react with different substances due to presence of different oxidation states, and they are transitional metals.." questions of haber process came tht ok, the graph was going backwards (down and curved) then explain by refering to exothermic reaction in equilibrium...
then the rest was ok then came, the question how can u say this is exothermic, here u just do those calculations, they even gave u the table for the numbers u need to use. u get answer negative (-530) which means its exothermic reaction.
then came test of sturation, and how water acted as base which was really easy. then cam the question of what happens when lactic acid is heated, the ans: acrylamide acid and water.
then the last page with calculations, first u get the answere for empirical formula as Mg3N2 (i can explain to u how if u want to know).
then the ans for the balencing of the equation:
Al4C3 + 12H2O --->4Al(OH)3 +3CH4
then last question the ans is: silicon is the limiting factor as fulride had 2 times the number of moles of silicon reacted so flourine was in excess.
teh number of moles of silicon fluride was:0.08 moles
now the only question i truly messsed up in was tht phosphate stuff, i must choose a metal tht doesnt dissove, and i must choose a metal tht has higher reactivity than sodium so it could be displaced. there fore i had problems and just wrote T3PO4. but u should also know tht this is not the reson to write. as they gave u tht graph for a reason, so u need to write tht hight of precipitate wise. so if u wrote the reson tht goes somethin like this "i must choose a metal tht doesnt dissove, and i must choose a metal tht has higher reactivity than sodium so it could be displaced", then i feel u messed up...
well ths all correct me if im wrong, alas those were my answeres
lol and guys just write hydrogen chloride had a lower pH than hydrogen fluride. and how to test if those acrylamide stuff had acid, just add metal carbonat and if effevecence was shown due to libbiration of carbon dioxise (which turns lime water milky) then it contained acid group, they wanted an answer which has nothing got to do with an indicator.
goin4dakill:
Hey Sneakerz.. Your answers seem pretty decent. I dont know if this is correct or not, but I think Bromine was a limiting factor..
The equation was
Si + 2Br2 ----> SiBr2
If we use the mole equations Moles= mass/Mr.. We rearange it to get 0.16*320.
O.16 because there are two moles of Bromine, and 320 for the Mr of Bromine. Our answer 51.2, therefore more than 25g. We would technically need that amount of Bromine..
My teachers said something along the same line. Dont worry though! It was like 2 marks!
I know people said that we should stop attacking eachother and who is right or wrong..because what is done is DONE! We really should start on physics..but the truth is this is a board to "Discuss Chemistry Paper 3"..So yeah.
On the last page there was also a question..where you had to balance it..and it qas 0.03 moles..and then 0.09 and 0.12 or something..How on earth did u do that. I couldnt balance it for my life..i always had to many oxygens.. :/
Hope you all did well!!!
girl_92:
--- Quote from: Roxy on June 02, 2009, 12:14:17 am ---yeah I think it dus.... it decolourises it ....i think ..:P
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no it only removes chlorophyll from leaves does not decolourise it
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