Question

Why is cathode in an electrolytic cell considered to be negative and anode positive?

Answer 1

Electrode which attracts positive charge particles which we called cation forms cathodic compartment of electrolytic cell and anode is a compartment having an electrode which will attract the negative charged ions anions towards it. In some reactions a salt bridge is used having potassium chloride solution in it.

Complete step-by-step answer: For making an electrolytic cell we want two electrodes which if immersed in liquid they can act as an electrons suppliers. These can be made up of graphite mostly, many electrodes are made up of it and also stainless steel or platinum. These electrodes are dipped into the solution which is capable of conducting electricity. Let’s consider an example where we have two beakers containing solutions which are capable of conducting electricity or we can say that they are able to pass electrons from them. Now there are two conditions which an electrode can undergo, the negatively charged electrode will attract the positive ions from the solutions which we called cathode. It will attract ions by giving excess of its electrons hence we can call it having reducing agent like property. So in an electrolytic cell, if any electrode is having such properties of attracting cations towards it, we call it “Cathode”.
Now if we talk about an electrode such that it has properties to attract the negative ions (anions) towards it, we call it anode. Now if we want to set a reaction cell, it will be made up of two half-cells. The substances which are having high reducing potential, it will form cathode and if any substance has lesser value of reduction potential also negative values it forms the anode part.

Note: The cathodic and anodic compartment are exactly opposite when we talk about the case of zinc and copper. We call it a galvanic cell, in that cell zinc $Zn$ makes the anodic compartment it means it has electrodes which will attract the negative ions towards it and the cathodic compartment is formed by copper $Cu$.