Question

Which of the following electrolytes will have maximum coagulating value for
AgI/Ag+
sol?
(i) Na2S
(ii) Na3PO4
(iii) Na2SO4
(iv) NaCl


NCERT Class XII
Chemistry - Exemplar Problems

Chapter 5. Surface Chemistry

Answer 1

The answer is: (ii) Na3PO4

Answer 2

The electrolytes which have maximum coagulating value for $\bold{\frac{A g I}{A g^{+}} sol}$ is $\bold{(ii) Na_3PO_4}$

Explanation:

According to Hardy - Schulz law, as the valence of flocculating ions increases, the coagulating power of ions also increases.

The coagulation power depends on charge of the ions. As the charge increases, the coagulation power also increases. Since $Ag^{+}$ ions have +1 charge, so we need more charge to coagulate the ions.

In the given option, $\mathrm{Na}_{3} \mathrm{PO}_{4}$ has $\bold{\mathrm{PO}_{4}^{-3}}$ ion which has maximum charge, hence it will have maximum coagulating value for $\frac{A g I}{A g^{+}}$.