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Analytical Chemistry
The following table shows the tests a student performed on four different aqueous solutions which are X, Y, Z and W. based on the observation provided identify the cation present:
|
Chemical Test |
Observation |
Conclusion |
|
To solution X, ammonium hydroxide is added in minimum quantity first and then in excess. |
A dirty white precipitate is formed which dissolves in excess to form a clear solution |
|
|
To solution Y ammonium hydroxide is added in minimum quantity first and then excess. |
A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution |
|
|
To solution W a small quantity of sodium hydroxide solution is added and then in excess. |
A white precipitate is formed which remains insoluble. |
|
|
To a salt Z calcium hydroxide solution is added and then heated. |
A pungent smelling gas turning moist red litmus paper blue is obtained. |
|
|
Chemical Test |
Observation |
Conclusion |
|
To solution X, ammonium hydroxide is added in minimum quantity first and then in excess. |
A dirty white precipitate is formed which dissolves in excess to form a clear solution |
Zn2+ |
|
To solution Y ammonium hydroxide is added in minimum quantity first and then excess. |
A pale blue precipitate is formed which dissolves in excess to form a clear inky blue solution |
Cu2+ |
|
To solution W a small quantity of sodium hydroxide solution is added and then in excess. |
A white precipitate is formed which remains insoluble. |
Ca2+
|
|
To a salt Z calcium hydroxide solution is added and then heated. |
A pungent smelling gas turning moist red litmus paper blue is obtained. |
NH4+ |
Distinguish between the following pairs of compound using the test given within brackets:
Iron(II) sulphate and iron(III) sulphate (using ammonium hydroxide)
Iron (II) sulphate gives dirty green ppt with ammonium hydroxide insoluble in excess.
Iron (III ) sulphate gives reddish brown ppt with ammonium hydroxide insoluble in excess.
State your observation in the following case:
When excess sodium hydroxide is added to calcium nitrate solution.
When an excess of sodium hydroxide is added to calcium nitrate solution then, a white ppt of Ca(OH)2 is obtained that remains insoluble in excess of NaOH.
State the inference drawn from the following observations:
i) On carrying out the flame test with a salt P a Brick red flame was obtained. What is the cation in P?
ii) A gas Q turns moist lead acetate paper silvery black. Identify the gas Q.
i) calcium ion( Ca2+)
ii) Q = hydrogen sulphide gas (H2S)
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Mock Test Series
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