IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: Naruto on May 12, 2009, 11:04:28 am
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hey guyz i have a big problem in chemistry subject and i am really confused about one question from the past paper (paper 6, 2003 nov and Q 6).... it is the Plan an experiment question and in the mark scheme they didnt answered properly... i mean they didnt mention any apparatus used.. so i need a proper answer for this quesion. hope you will help me!!
Thanx
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helloooooo is there anyone!! >:(
or no one know it too... ???
hello where is astar, sweetsh, and unoxou... where are you guyz!!
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it's very easy. Take the three samples of coal (they must be of equal weight) and put each sample in a testube. Close the testube with a bung and attach a delivery tube to the testtube. fill a beaker with potassium dichromate solution and the end of the test tube must be put inside it (only put inside after starting to heat the coal for a minute). Heat the testube containing the coal sample. Measure the time taken for the potassium dichromate to turn green. Repeat the experiment with the other samples. The sample which produces the fastest colour change release the most volume of sulphur dioxide.
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@ godfather
thankx man for answering, but i have some problem with your answer is that you said to heat the coal but in the mark scheme they sid to burn it and not to heat it...... because burning with oxygen will produce sulphur dioxide and heating does not.... so i dont understand one thing that how we will collect the gas when we burn some thing???????
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when u burn a fossil fuel such as coal, etc it automotically produces gases...or releases fumes...and u collect it by upward or downward delivery in a test tube or something ??? i GUESS?
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for that o/n 2003 question:
answer: same masses of crushed coal are placed in three crucibles. a bent tube is connected from each pot to three conical flsks containing equal volumes of potassium decromate (vi). each coal sample is burnt by subjecting it to heat from a bunsen burner. the crucibles may be covered with lids to prevent escape of gases, with one hole in the lid to fit bent tube.as coal sample burns, the gas evolved reaches the potasiium dichromate (vi) solution. the heat supply is immeaditly stopped as the solution changes colour from orange to green.the new masses of the burnt coal is found and subtracted from the initial masses. the least value obtained from a coal sample is the one which produces most sulphur dioxide gas.
(ofcourse some of u may choose 2 measure the time for colour change instead of finding the masses.in this case the one with the least time would b the coal producing the highest amount of SO2) :)
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@ sweetest angel
thanx!!! :D for your answer it really had removed all the question from my mind.....thanx again
@angell
thank u too for replying to my question :)
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hey guyz i have one more question??? hope that this time i will also have a good feedbacks/respond...
the question is that
'a grass is crushed with sand and is than ground with enthanol until the solution is saturatred and grass contain green pigment chlorophyll' so the question is that "Suggest why the grass is ground with the ethanol rather than water??"
hope you guyz will answer me
thanx:)
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HELLOOOOOOOOO !!!!!! >:(
Is there anyone who can answer my question????????????
well i heard that this site can solve all of our problems but now i think that it was all rubbish!!! >:(
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tell me which year..i can answer u nw bt tellin' me where's da question mkes tings easier
;)
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hey guyz i have one more question??? hope that this time i will also have a good feedbacks/respond...
the question is that
'a grass is crushed with sand and is than ground with enthanol until the solution is saturatred and grass contain green pigment chlorophyll' so the question is that "Suggest why the grass is ground with the ethanol rather than water??"
hope you guyz will answer me
thanx:)
Ans: because chlorophyll is more soluble in ethanol
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@A.Am
thanx :)
@sweetest angel
the year is (Nov 2005 question no. 3)
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I am really scared of the last q in every year
it's 6 marks and it's hard
If we get a hard one tomorrow then it will be bad
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@ yasser37
i totally agree with you that question is sometime hard but if we study parcticle technique chapter and preparation of salt than it is easy!!
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practical technique chapter??? whats that [oh nooo!!:(]
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Im sorry Naruto I couldnt access the forum at all.
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hey sweetsh no problem dont be sorry :)
i got the answers.. and i just wanna ask that how many papers should i practice for both chemistry paper 6 and english paper 2
any suggestions.. :)
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Hi
Does any one tell me where i can find chemistry 9256/6 nov 2000 paper.
thanks
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www.freeexampapers.com ?!
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hey sweetsh no problem dont be sorry :)
i got the answers.. and i just wanna ask that how many papers should i practice for both chemistry paper 6 and english paper 2
any suggestions.. :)
The more you practice the better your situation will be. Thats what im doing, solving past papers.
And what subject is the paper 2 you mean english as a 2nd language or english language