Question

1. a.) Some hydroxides such as Zn(OH)2 have increased solubility in both acidic and basic solutions. Fully explain this phenomenon and use relevant chemical reactions to help your explanation.

b.) why does the pH affect solubility of CaF2 but not CaCl2?

Answer 1

in acidic:

H+ ions are present, therfore, they react with OH- ions to form H2O, therefore the shift:

Zn(OH)2 <--> Zn+2 and 2OH-

is displaced toward Zn+2

for basic solution, this is true since Zn will form complex such as zincate i.e. Zn(OH)4 instead of OH2

this is therefore favoured toward Zn(OH)4 produciton, therefore Zn(OH)2 will seem to dissapear

b)

pH = H+ concnetation

CaF2 = Ca+2 and 2F-

H+ and F- = HF

then solubility increassins since Ca+2 will increase in solution

for CaCl2 = Ca+2 and 2Cl-

H+ and Cl- are not going to form Hcl since this is a sTRONG acid