Question

On additon of which metal the blue coloured copper sulphate solution turns into colourless solution?

• A. $\mathrm{Ag}$
• B. $\mathrm{Hg}$
• C. $\mathrm{Zn}$
• D. $\mathrm{Au}$

Answer 1

The correct option is C

$\mathrm{Zn}$

A reduction potential measures a molecule's tendency to be reduced by accepting additional electrons.

The element's tendency to form positive ions increases as its standard reduction potential value decreases. When Copper ($\mathrm{Cu}$) will be reduced from the solution, it becomes colorless.

The standard reduction potential for Copper ($\mathrm{Cu}$) is $0.34\mathrm{V}$

Explanation for the correct option:

(C) Zinc ($\mathrm{Zn}$): The standard electrode potential of Zinc ($\mathrm{Zn}$) is $-0.76\mathrm{V}$. The standard reduction potential of Zinc ($\mathrm{Zn}$) is less than Copper ($\mathrm{Cu}$), so it will replace the Copper ($\mathrm{Cu}$) ions from the Copper sulphate (${\mathrm{CuSO}}_4$) solution to give Zinc sulphate (${\mathrm{ZnSO}}_4$)which is colorless.

Explanation for the incorrect option:

Silver, mercury and gold are less reactive than copper thus they can not replace copper from its salt.

Therefore, the correct option is (C).