a Explain what the common ion effect is and give an example

a) Explain what the common ion effect is and give an example. b) Explain why the common ion effect keeps the equilibrium shifted to the reactant side in a buffer solution. c) Calculate the [HF] and [F] in a solution of 0.10 M HF d) Calculate the [HF] and [F] in a solution containing of 0.10 M HF and 0.10 M NaF. e) Explain why the solution in part c is not a buffer solution while the solution in part d is a buffer solution.

Solution

a) common ion effect:

the decrease in solubility of an electrolyte or decrease in ionisation of weak electrolyte by the addition of strong electrolyte having commonion is called common ion effect.

NH₄ OH <=========> NH₄⁺ + OH^- (slow ionisation)

NH₄ Cl <=========> NH₄⁺ + Cl^-   ( compleate ionisation)

b) to the above example in solution concentraction of NH₄⁺ ions are increases, they will react with  OH^- ions and backword reaction takeplace. so the equilibrium shift in to reactant side.

c) 0.1 M HF means solution having 0.1 M H⁺ AND 0.1 M F^- ions, so

concentraction of HF is 0.1 and   F^- is 0.1 M

d) concentraction of HF is 0.1 and concentraction of F^- is 0.1+0.1 =0.2M

e) in case of solution C , it is normal but in case of f solution D, it is acidic buffer solution.

it having weak acid and its strongn conjugate salt. this type of mixture is not in solution C.