Question

Which salts will be more soluble in an acidic solution than in pure water?

PbI2

AIPO4

Zn(OH)2

RbClO4

SrSO4

Answer 1

• The salt dissolve in aqueous medium into costituent ions.
• If at least one of the constituent ion is reacting with water or other available ions and converting into a non-ionic compound (wek electrolyte) such a salt said to more dissolved.
• This is because as one the constituent ions formig salt is no more in solution, the recombination of constituent ions would not occur.

The ionization and subsequent disolution of salts is as,

Options rulled:

For AlPO4, RbClO4, SrSO4 salts

AIPO4 (aq) Al³⁺ (aq) + PO₄^3- (aq)

In acidic medium,

Al³⁺ (aq) + PO₄^3- (aq) + 3H⁺ (aq) Al³⁺ (aq) + H₃PO₄(aq)

H₃PO₄(aq) is strong acid an eventully ionizes back to PO₄^3- (aq) hence option is rulled out.

3. RbClO⁴ Rb⁺ (aq) + ClO₄^- (aq)

Rb⁺ (aq) + ClO₄^- (aq) + H+ (aq) Rb⁺ (aq) + HClO₄(aq)

In acidic medium it gives HClO4 which is strong acid and eventually gives ClO4- back hence ruled out.

SrSO4 Sr²⁺ (aq) + SO₄^2- (aq)

in acidc medium,

Sr²⁺ (aq) + SO₄^2- (aq) + 2H⁺ (aq) Sr²⁺ (aq) + H₂SO₄ (aq)

H₂SO₄ is againn strong acid and eventually gies SO₄^2- ions back for recombination hence rulled out.

2)

PbI₂ (aq) Pb²⁺ (aq) + 2 I^- (aq)

Pb²⁺ (aq) + 2 I^- (aq) + 2 H+   Pb²⁺ (aq) + 2 HI (aq)

HI is weak acid hence obviously in acidic medium solubility of PbI2 will be more.

But in Zn(OH)2 case

Zn(OH)2 (aq) Zn²⁺ (aq) + 2 HO^- (aq)

In acidic medium

Zn²⁺ (aq) + 2 HO^- (aq) + 2 H⁺ (aq) Zn²⁺ (aq) + H₂O (aq)

H2O is far weak electrolyte than HI and hence almost once formed will not give back HO^-.

This sets Zn2+ ions freely dissolved state and hence the solubility.

Answer: Zn(OH)2 in acidic medium will be most soluble salt.

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