Which of the following reagents will increase the solubility of PbF 2 ? Assume e

Question

Which of the following reagents will increase the solubility of PbF2? Assume each reagent has a large concentration.

A. NaF

B. HCl

C. NaOH

D. Pb(NO3)2

I understand that A and D are incorrect because os the common ion effect, but I am unsure as to why B and C are both correct. Could someone please explain?

Also, I have no understanding of this question. How is it possible to even decide:

The molar solubility of _______ is not influenced by the pH of the solution.

A. Na3PO4

B. NaF

C. KNO3

D. AlCl3

E. MnS

Explanation / Answer

1. PbF2 a base F-

it dissociates as:

PbF2 --> Pb+2 + 2F-

If we add H+ it will react with F- to give HF.

So the equilibrium will shift towards right hand side and hence solubility of PbF2 increases.( option B, HCl)

2. As shown above the salt having a strong conjugate base will be influenced by change in pH, lesser the pH ( more the acidic solution) more the solubility of salt.

However salt in which we have weak conjugate base ( base of strong acid) like Cl- , NO3- , Br- etc will not be affected by change in pH.

so for AlCl3, And KNO3 the solubility will not be affected by pH.

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