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.

Distinguish between the following pairs of compound using the test given within brackets:

Iron(II) sulphate and iron(III) sulphate (using ammonium hydroxide)

State your observation in the following case:

When excess sodium hydroxide is added to calcium nitrate solution.

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.