Question

A. Calculate the ionic strength of an aqueous solution of 0.037 M KCl. B. How will the activity of 0.025 M Ca2+ be impacted by the addition of 0.050 M KCl? In other words will the activity of Ca2+ increase or decrease when KCl is added to pure water? Briefly explain your answer.

Answer 1

A 2 concentration of Kee is 0.037(M) We know the expression of Yonie Strength 1 = 1 { C; 2; So C- Concentration z = Change of Aere [ki] = 0.037 (M) ian [ee] = 0.037 (19) C ofion M = 2 [ext 12 + Ce-12] or 4 = ₂ [ 0.037 + 0.037) a la 0:037 So, ionic K 1 Strength is 0.037. rengt B. We know from Delye Hückel theory that the mean ionic activity coefficient of a Salt decreases with increase in lonic strength - log8+ = = AZ + Z. V M. I f o.osom kel is added then ionic Strength (en increases and activity coefficient (8+).

decreases, We know that activity (a) = activity coefficient (84) X Concen -tration a =(8+). C fr. a cat = ft. Ceat Since 8+ (activity coefficient decreases so activity of cat also decreases.