Tests were carried out an a salt X. The table below summarizes the results of the tests.
TestObservation1) Appearance of XWhite solid2) Addition of dilute HCl to X.Any gases given off were tested.X dissolved to form a colourless solution.A choking smell gas was detected3) flame testLilac flame4) X dissolved in water and was divided into two equal portions.i) to the first portion, an equalvolume of aqueous sodium hydroxide was added.Than add excess NaOH(aq)ii) To the second portion, acidified potassium dichromate solution was added. NO observable change NO observable changeThe colour of dichromate change from orange to green.
a) what is your deduction of X from the test (1) ?b) what is your deduction of X from the test (2) ?c) what is your deduction of X from the test (3) ?d) what is your deduction of X from the test (4i) ?e) what is your deduction of X from the test (4ii) ?f) suggest the identity of X.
chemistry urgent!!!
2011-02-27 9:57 pm
回答 (3)
2011-02-28 1:56 am
✔ 最佳答案
I think I need to add and correct something from yu 's answersa)not contain Fe2+, Fe3+, Cu2+ ion
--it is not enough, from the result, we know that X contains colourless
ions, and Fe2+, Fe3+, Cu2+ are just examples of those
b)add dil acid to give choke smell mean it react with acid to give out sulphur dioxide gas, that deduce the salt contain sulphite anion.
--I thought for quite long and I agree with yu that the gas should be sulphur
dioxide
--it dissolves to form colourless soultion, so it should be of colorless ions
--there are some other gas that can give a choking/irritating smell, like
nitrogen dioxide and ammonia gas, you need to observe the color of the
gas (NO2 is yellowish brown and SO2 is colorlese) and test it by wet pH
paper(ammonia is alkaline while SO2 is acidic)
c)it contain potassium cation which give lilac flame colour in flame test
--it is correct
d)it should be potassium ion , sodium ion or ammonium ion
--it should be "it forms water-soluble metal hydroxide", again , the above ions
are just examples,Ca2+ can also be an example
e)it is a reducing agent which can change dichromate colour
--actually, dichromate ion is Cr2O72- , which is orange in color, but in the
end, it becomes green (which is the color of chromium(iii) ion), so it loses
oxygen(be reduced)
f)X is potassium sulphite, KSO3
--actually it should be K2SO3 , SO3 ion is of 2-, so it needs 2K (of 1+)
--also, it may be K2SO4 ( which is also a white solid)
2011-02-27 17:59:51 補充：
a).....Fe2+, Fe3+, Cu2+ are just examples of those colored ions
b)......(NO2 is yellowish brown and SO2 is colorless)
sorry for the mistake
參考: myself, myself
2011-02-28 1:01 am
formula, what's formula of potassium sulphite?
o well, why cannot be potassium hydrogensulphite?
o well, why cannot be potassium hydrogensulphite?
2011-02-27 11:58 pm
a)not contain Fe2+, Fe3+, Cu2+ ion
b)add dil acid to give choke smell mean it react with acid to give out sulphur dioxide gas, that deduce the salt contain sulphite anion.
c)it contain potassium cation which give lilac flame colour in flame test
d)it should be potassium ion , sodium ion or ammonium ion
e)it is a reducing agent which can change dichromate colour
f)X is potassium sulphite, KSO3
b)add dil acid to give choke smell mean it react with acid to give out sulphur dioxide gas, that deduce the salt contain sulphite anion.
c)it contain potassium cation which give lilac flame colour in flame test
d)it should be potassium ion , sodium ion or ammonium ion
e)it is a reducing agent which can change dichromate colour
f)X is potassium sulphite, KSO3
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