Electrolysis of solutions

Electrolysis of solutions

Ions are free to move in solution of the compounds. But sometimes we cannot get a metal because of its highly reactivity. This is because of water in the solution. Water molecule effects the electrolysis.

When solutions are electrolyzed, hydrogen being a non – metal, is deposited on cathode.

Because hydrogen is an exceptional case, donate 1 electron per hydrogen atom.

H⁺        +     e^-       à         H

But hydrogen is a diatomic molecule

So

2H⁺        +     2e^-       à         H₂

Why is hydrogen given off?

We know water molecules are present in solution. Take any solution from table 7.6, For example calcium nitrate, water molecule will also split into H⁺ &  OH^-

       H₂O                     H⁺      +       OH^-

So hydrogen is deposited at cathode along with calcium. Calcium is more reactive & stable than hydrogen, replaces it & kicks out from cathode.

At cathode:

2 H⁺        +     2e^-       à         H₂

At anode:

4 OH^-        -     4e^-       à      2H₂O   +      O₂

 

                   Class Assessment

1.  Ions are free to move in solution of the compounds. T

2.  Hydrogen being a non – metal, is deposited on cathode. T

3.  Hydrogen is a monoatomic molecule. F

4.  Calcium is more reactive & stable than hydrogen. T