Question

The Effect of a Common Ion on Molar Solubility: pH and OH^- as a Common Ion

We have seen from our study of acid/base chemistry that the presence of a weak base such as ammonia (K_b = 1.8 X 10^-5) can affect the pH of an aqueous solution. This pH can in turn affect the solubility of a metal hydroxide salt as a result of the common ion effect. The Ksp for manganese (II) hydroxide = 2.0 X 10^-13. What is the molar solubility of manganese (II) hydroxide in a 4.00M solution of ammonia?

4. -/2 pointsGVSUChem116v2 15.c.3.P002. My Notes + Ask Your Teacher The Effect of a Common Ion on Molar Solubility: pH and OH as a Common Ion We have seen from our study of acid/base chemistry that the presence of a weak base such as ammonia (Kb = 1.8 X 10-5) can affect the pH of an aqueous solution. This pH can in turn affect the solubility of a metal hydroxide salt as a result of the common ion effect. The Ksp for manganese (II) hydroxide = 2.0 X 10-13. What is the molar solubility of manganese (II) hydroxide in a 4.00M solution of ammonia?

Answer 1

solubility on " general; addition of common ion decreases a sparingly soluble salt like Mn(OH)₂ Thus; NHQ + Hoo NHU A OH kg = [Nha Tot] - [NHg] As [ N Ha] = lot we can write; kb = [ot] { given INHg] = 4:00] 4.00 08 [olt 7² = 4 x 1.8 x 10-5 0 [ot] = √7.2x10-5 or [H] = 8.48x10-3 Now; for Mn. 10H ; MNOH)₂ ~ Mn² + 2011 Ksp = [Mn?'][011] of c be the solubility of MN (OH)2; (Mn2+] = ( x [5t1 = 20 et 8. 48x10-3 Ksp = c(21+8:48 x 10.3) * or 2x10-13 (120+ 8.48 x 10-3)? Quite obviously ele [ot] . Hence, we can write 2x 10-13 (18.48 X 10.9) 2 2x 10-1 2 x 10-13 4.2 x 105 1 2 .99x10-09 presence of Hence; solubility is 2.77 x 10-9 (M) in NHS