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If a question says 'prepare a series of tests to identify compounds X, Y and Z', am I not allowed to say take a sample from each? That way a HCl test wouldn't interfere with a silver nitrate test. Or must I plan out successive experiments which won't interfere with each oother?
Original post by rishoo1
If a question says 'prepare a series of tests to identify compounds X, Y and Z', am I not allowed to say take a sample from each? That way a HCl test wouldn't interfere with a silver nitrate test. Or must I plan out successive experiments which won't interfere with each oother?

you can say take a sample from each, often in mark schemes it doens't even mention how ur preparing or sorting out the samples they're just interested in the actual tests and results
Original post by rishoo1
If a question says 'prepare a series of tests to identify compounds X, Y and Z', am I not allowed to say take a sample from each? That way a HCl test wouldn't interfere with a silver nitrate test. Or must I plan out successive experiments which won't interfere with each oother?

You can do either.

The trick with successive tests for anions is to first add nitric acid. If there is no effervescence, then add barium nitrate. If there is no precipitation, then add silver nitrate. You can get away with this as all nitrates are soluble and so only introducing only nitric acid and nitrates, you don’t add anything that could cause a false positive.

I personally would just do separate tests on portions of each sample as then it gives you more freedom with the reagents you try (e.g BaCl2/HCl shouldn’t cause any problems) and it becomes more obvious how to test for both the anions and cations.
Original post by rishoo1
If a question says 'prepare a series of tests to identify compounds X, Y and Z', am I not allowed to say take a sample from each? That way a HCl test wouldn't interfere with a silver nitrate test. Or must I plan out successive experiments which won't interfere with each oother?


you dont have to say ‘take a sample from each’ just say the order that the tests are meant to be in.
1. ammonium test
2. carbonate test
3. sulfate test
4. halide tests
Reply 4
Original post by onlineaeyong
you dont have to say ‘take a sample from each’ just say the order that the tests are meant to be in.
1. ammonium test
2. carbonate test
3. sulfate test
4. halide tests

But can they interfere with each other
Original post by rishoo1
But can they interfere with each other

This is why you need to pick your reagents carefully.

See my post where I have explained why you use nitric acid and nitrates as the reagents if you are going to do successive tests. If you use nitric acid, barium nitrate and silver nitrate, provided you have done the NaOH tests for NH4^+ / Mg / Ca first, there shouldn’t be any issues.

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