Question

Colourless solution of the following four salts are placed separately in four different test tubes and a strip of copper is dipeed in each one of these. Which solution will turn blue?

• A. $KN{O}_3$
• B. $AgN{O}_3$
• C. $Zn(N{O}_3{)}_2$
• D. $ZnS{O}_4$

Answer 1

Answer: (B)

$AgN{O}_3$

Option (B) is correct.

$AgN{O}_3$ will turn the copper solution blue. Blue colour is due to formation of $C{u}^{2+}$ ions. Silver comes above copper in the electrochemical series. $Zn$ and $K$ are placed below copper in electrochemical series. Thus copper can displace silver ions from its salt solution but K and Zn cannot displace silver ions from its salt solution.