The following table shows the tests a student performed on four different aqueous solutions which are X, Y, Z and W. Based on the observations provided, identify the cation present :

Explanation

(i) The salt solution X contains `Zn^(2+)` ions.
(ii) The salt solution Y contains `Cu^(2+)` ions.
(iii) The salt solution W contains `Ca^(2+)` ions or `Mg^(2+)` ion.
(iv) Salt Z contains `NH_4^+` ions or ammonium ions.