C1V1 = C2V2

Where:

C1 = Initial concentration (0.2 N)

V1 = Initial volume (let's say V1 milliliters)

C2 = Final concentration (0.05 N)

V2 = Final volume (which we need to find)

Rearranging the formula to solve for V2, we get:

V2 = (C1 x V1) / C2

Substituting the given values:

V2 = (0.2 N x V1) / 0.05 N

V2 = 4 x V1

Therefore, to obtain 0.05 N KMnO4, you need to dilute your 0.2 N KMnO4 solution by adding 4 times its volume with distilled water. For example, if you start with 100 mL of 0.2 N KMnO4, you should add 400 mL of distilled water to obtain 500 mL of 0.05 N KMnO4.