Question

The following four colourless salt
solutions are placed in separate test
tubes and a strip of Cu is placed in each
solution which finally turns blue
(1) Zn(NO3)2 (2) Mg(NO3)2
(3) KNO3
(4) AgNO3
​

Answer 1

K[Cu(NO3)2] is blue is blue complex. So KNO3 is answer

Answer 2

Answer:

4. AgNO3

Explanation:

Zn, Mg, K, these are reactive metals.

Cu can displace with AgNO3 Sol". form Cu(NO3)2 blue color sol".