The following table shows the test a student performed on four different aqueous solution which are X, Y, Z and W. Based on the observations provided, identify the action 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 in 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 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.

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Solution

(i) The conclusion is $Z n^{2 +}$ ion is present. When $N H_{4} O H$ solution is added to $Z n S O_{4}$ we get white precipitate of $Z n (O H)_{2}$ .
$Z n S O_{4} + 2 N H_{4} O H \to (N H_{4})_{2} S O_{4} + Z n (O H)_{2}$
These white ppt dissolve in excess of $N H_{4} O H$ solution.
$Z n (O H)_{2} + 2 (N H_{4})_{2} S O_{4} + 2 N H_{4} O H \to [Z n (N H_{3})_{4}] S O_{4} + 4 H_{2} O$

(ii)The conclusion is $C u^{2 +}$ ion is present. The solution Y is copper sulphate solution. With $N H_{4} O H$ solution it gives pale blue precipitate of $C u (O H)_{2}$ .
$C u S O_{4} + 2 N H_{4} O H \to (N H_{4})_{2} S O_{4} + C u (O H)_{2}$
With excess $N H_{4} O H$ solution this solution turns deep blue in colour.
$(N H_{4})_{2} S O_{4} + C u (O H)_{2} + 2 N H_{4} O H \to [C u (N H_{3})_{4}] S O_{4} + 4 H_{2} O$

(iii) The conclusion is $C a^{2 +}$ ion is present. The solution W is calcium chloride solution. With NaOH solution it gives white precipitates of $C a (O H)_{2}$ which are insoluble in excess.
$C a C l_{2} + 2 N a O H \to 2 N a C l + C a (O H)_{2}$

(iv) The conclusion is $N H^{4 +}$ ion is present. The salt Z is ammonium chloride. With NaOH solution it libreates $N H_{3}$ gas which is alkaline in nature.
$N H_{4} C l + N a O H Δ \to N a C l + H_{2} O + N H_{3}$

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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 in 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 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.