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) `C-Zn^(2+)` (ii) `Y-Cu^(2+)`
(iii) `W-Ca^(2+)` or `Mg^(2+)`
(iv) `Z- NH_(4)`