Question

Derive the relationship between degree of dissociation and dissociation constant for weak electrolyte​

Answer 1

The relationship between degree of dissociation and dissociation constant for weak electrolyte is

α = √K/C

• First , write the chemical equation for the dissociation of weak acid -

HA ⇌ H+ + A-

At initial time ,t0 C 0 0

At time, t C(1-α) Cα Cα

• So , here at initial time t0 the concentration is C . After time t there is dissociation of weak electrolyte occurs slowly and the degree by which it dissociates is represent by α .

• So ,here α = degree of dissociation.

• Now , we have to write the dissociation constant for the above reaction.

Dissociation constant = [Product]/[Reactant]

K = Cα * Cα / C(1-α)

K = Cα² / 1 - α

• If the value of α is very small as compared to the 1 then we can neglect it's value.

So, K = Cα²

α = √K/C