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CHEMISTRY PAPER 3 DOUBTSS!!

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Guys, how do we distinguish between hydrogen and oxygen with our observations? Like i doubt i'll have time to carry out the actual tests so like how will i know which gas it is? If like OH then what would it be?
The sequence of gas tests? We can distinguish ammonia due to its smell but, how about the others?
guys it depends on the reagents you are using... Since the question paper guides us thoroughly, for instance, if we are asked to use Al foil and OH- then we can expect NH3 only, no other gas gets liberated with Al and OH-. If we are using dilute acids, then it could either be CO2 or SO2, if you are using dilute acids, keep a strip of filter paper moist with potassium manganate (VII), place the bung on test tube and wait for gas to collect, then test for SO2, if it's negative, you can immediately put the delivery tube of limewater, I think we get that ready-made. NO is also liberated by dilute acids, but since it immediately oxidizes to NO2, the brown color is evident.
And O2 is given off when we use H2O2 and H2 if we are using metal+ acid.
 
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There's this test which includes adding acidified KMnO4(aq) followed by aqueous starch. Does anyone know the purpose for this?
Can you quote the particular question? Because starch may have some purpose in that particular instance but if manganate ions are used, and the solution turns from purple to colorless, then it's because of sulfite ions. Basically the sulfite ions get oxidized to sulfate ions because potassium manganate (VII) is an oxidizing agent, it will oxidize the sulfite and itself get reduced, when it gets reduced, it decolorizes, so it indicates that sulfite is the anion present.
 
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guys it depends on the reagents you are using... Since the question paper guides us thoroughly, for instance, if we are asked to use Al foil and OH- then we can expect NH3 only, no other gas gets liberated with Al and OH-. If we are using dilute acids, then it could either be CO2 or SO2, if you are using dilute acids, keep a strip of filter paper moist with potassium manganate (VII), place the bung on test tube and wait for gas to collect, then test for SO2, if it's negative, you can immediately put the delivery tube of limewater, I think we get that ready-made. NO is also liberated by dilute acids, but since it immediately oxidizes to NO2, the brown color is evident.
And O2 is given off when we use H2O2 and H2 if we are using metal+ acid.
Wow thats really helpful thankyouuuuuuuuuuu!!!!
 
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I
Can you quote the particular question? Because starch may have some purpose in that particular instance but if manganate ions are used, and the solution turns from purple to colorless, then it's because of sulfite ions. Basically the sulfite ions get oxidized to sulfate ions because potassium manganate (VII) is an oxidizing agent, it will oxidize the sulfite and itself get reduced, when it gets reduced, it decolorizes, so it indicates that sulfite is the anion present.
Realised that it was being used as a test for the presence of Iodine. ( color change to blue-black on addition of starch)
 
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why not

Is this fine?
attachment.php
 
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this is the end of cambridge's standard...
Students know the answers before reading the question paper
We really proved ourselves an 'honest' nation
We dont really know it,its not that we know the paper,Its just a guess and guesses are never accurate,its not that we are just going to write on paper without performing.
 
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