Question

A strip of copper is placed in four different colourless salt solutions. They are:

$KN{O}_3,AgN{O}_3,Zn(N{O}_3{)}_2,Ca(N{O}_3{)}_2$.

Which one of the solutions will finally turn blue?

• A. $Ca(N{O}_3{)}_2$
• B. $KN{O}_3$
• C. $AgN{O}_3$
• D. $Zn(N{O}_3{)}_2$

Answer 1

The correct option is C $AgN{O}_3$

A typical reaction with silver nitrate is to suspend a rod of copper in a solution of silver nitrate, and leave it for a few hours. The silver nitrate reacts with copper to form hair like crystals of silver metal and a blue solution of copper nitrate.

$2AgN{O}_3+Cu\to Cu(N{O}_3{)}_2+2Ag$

Copper is unable to displace potassium, calcium and zinc from their nitrate solution which are higher than copper in the activity series.