colourless salt `(A) underset(740^(@)C) overset(Delta)to (B) +(C ) overset(Cu^(2+),Delta)to` blue coloured bead (D)
Identify the compound (A),(B),(C ) and (D).

Explanation

`underset((A))(Na_(2)B_(4)O_(7)).10H_(2)O underset(740^(@)C) overset(Delta)to underset((B+C))(2NaBO_(2))+B_(2)O_(3) overset(Cu^(2+), Delta)to underset(("Blue bead"))(Cu (BO_(2))_(2))`