Question

Compare the solubility of Mn(OH)2 (Ksp = 1.6x10-13)in the following solutions: Pure water, A solution buffered to be pH = 6.5 A solution buffered to be pH = 3.5 Compare the solubility of Mn(OH)2 (Ksp = 1.6x10-13)in the following solutions: Pure water, A solution buffered to be pH = 6.5 A solution buffered to be pH = 3.5 Pure water > pH 3.5 > pH 6.5 (least soluble) pH 3.5 > pH 6.5 > pure water (least soluble) pH 3.5 > pure water > pH 6.5 (least soluble) Pure water > pH 6.5 > pH 3.5 (least soluble) pH 6.5 > pH 3.5 > pure water (least soluble)

Answer 1

The order will be:

pH 3.5 > pH 6.5 > pH 7

Step-by-step explanation:

The solubility equation for Mn(OH)₂ is:

`Mn(OH)_(2)--->Mn^(+2)+2OH^(-)`

As per the reaction, Mn(OH)₂ is giving hydroxide ions

The given conditions are

a) Pure water = here the pH of water is 7.

[OH⁻] = 10⁻⁷ M

b) pH = 6.5

pOH = 7.5

[OH⁻] = 3.16 X 10⁻⁸ M

c) pH = 3.5

pOH = 10.5

[OH⁻] =3.16 X 10⁻¹¹ M

Thus from the three solutions and water the maximum concentration of hdyroxide ion is in pure water, hence the Mn(OH)₂ will be least soluble in it.

More the concentration of hydroxide, lesser the solubility of Mn(OH)₂

Order will be

pH 3.5 > pH 6.5 > pH 7