Question

Assertion: $A{{g}_{2}}S$ Is much less soluble in water than $A{{g}_{2}}O$ .
Reason: ${{S}^{2-}}$ Is much larger than ${{O}^{2-}}$ ; so polarization of ${{S}^{2-}}$ is higher than ${{O}^{2-}}$.
a.) The Assertion is true, Reason is true and Reason is the correct explanation for Assertion.
b.) The Assertion is true, Reason is true and Reason is not the correct explanation for Assertion.
c.) The Assertion is true, Reason is false.
d.) The Assertion is false, Reason is true.

Answer 1

Hint: Try to analyze the change of polarization with change in the size of the anion, which relates to the covalent nature of the compound. Also analyze how solubility changes with the polarization.

Complete step by step solution:
Given compounds are $A{{g}_{2}}S$ and $A{{g}_{2}}O$ in which the anions are ${{S}^{2-}}$ and ${{O}^{2-}}$
The size of ${{S}^{2-}}$ anion is much larger when compared to ${{O}^{2-}}$ anion, because the atomic number of the oxygen is 8 whose electronic configuration is $1{{s}^{2}}2{{s}^{2}}2{{p}^{4}}$ whereas the electronic configuration of the sulfur atom is $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{4}}$ possessing the atomic number as 16, it shows that the electrons present in the oxygen atom are less than the sulfur atom and hence the size of the sulfur is larger when compared to that of the oxygen.
Hence the size of the anion ${{S}^{2-}}$ is also larger than ${{O}^{2-}}$ ion
When the size of the anion increases then the polarization of the anion increases which increases the covalent character of the compound, when the covalent character increases then the solubility of the compound in the polar solvent decreases.
This says that the above given Assertion is correct and the reason is the correct explanation.
 Therefore the Assertion is correct, Reason is also correct and the Reason is the correct application of the Assertion.
So, the correct answer is “Option A”.

Note: We need to take care while answering this type of question. We need to have the correct explanation along with the correct answer (given Assertion), most of us will make mistakes with the reason part only which we have analyzed carefully, so that the reason we have should be perfect for the given Assertion.