Question

which of the solutions willl see an increase in solubility with an increase in ph?

A) BaF2

B)PbBr2

C)NaBr

D)Fe(OH)3

and how did you find your answer?

Answer 1

A)

BaF2 ----> Ba+2 + 2F-

2F- + 2H+ ---> 2HF

the equilibrium reaction is

BaF2 + 2H+ ---> Ba+2 + 2HF

given an increase in pH

it means decrease in the conc of H+

now

according to Le Chatlier principle

the equilibrium will shift in a direction to counter the change

As there is a decrease in H+ conc ,

the equilibrium will shift to increase the conc of H+

so

the equilibrium will shift to the left , which reduces the solubility of BaF2

so

the solubility of the BaF2 decreases with increase in pH

b) the same applies to PbBr2

the solubility of PbBr2 decreases with increase in pH

c)

similarly

the solubility of NaBr decreases with increase in pH

D) consider Fe(OH)3

Fe(OH)3 ---> Fe+3 + 3OH-

given an increase in pH

it means increase in the conc of OH-

now

according to Le Chatlier principle

the equilibrium will shift in a direction to counter the change

As there is a increase in OH- conc ,

the equilibrium will shift to decrease the conc of OH-

so

the equilibrium will shift to the left , which reduces the solubility of Fe(OH)3

so

the solubility of the Fe(OH)3 decreases with increase in pH