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 The solubility product of a sparingly soluble salt \mathrm{A}_{2} \mathrm{X}_{3} \text { is } 1.1 \times 10^{-23} . If specific conductance of he solution is 3 \times 10^{-5} \mathrm{Sm}^{-1}, the limiting molar conducivity of the solution is x \times 10^{-3} \mathrm{~S} \mathrm{~m}^{2} \mathrm{~mol}^{-1}. The value of x is _______.

Option: 1

3


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

Let the solubility of \mathrm{A_{2} X_{3} } be \mathrm{s ~mol L^{-1} }.

We have, 

\mathrm{A_{2} X_{3} \longrightarrow 2 A^{3+}+3 X^{2-}}

                        \mathrm{2s \quad \; \; \; \; \; \; 3s}

\mathrm{k_{s p} \text { of } A_{2} X_{3}=(2s)^{2}(3s)^{3}}

\mathrm{1.1 \times 10^{-23}=108s^{5}}

\mathrm{s=1 \times 10^{-5} \mathrm{~mol} / \mathrm{L}}

\mathrm{s=\frac{10^{-5}}{10^{-3}} \mathrm{~mol} / \mathrm{m}^{3} \quad\left(1 \mathrm{~L}=10^{-3} \mathrm{~m}^{3}\right)}

\mathrm{s=10^{-2} \mathrm{~mol} / \mathrm{m}^{3}}

Now for a sparingly soluble salt, 

\mathrm{\Lambda _{m}^{\infty }=\frac{K}{C}~Sm^{2}mol^{-1}}\; \; \; \; \; \; \; \left [ \text{all terms in SI units}\right ]

\Lambda_{m}^{\infty}=\frac{3 \times 10^{-5}}{10^{-2}} \mathrm{~Sm}^{2} \mathrm{~mol}^{-1}\\

\Lambda_{m}^{\infty}=3 \times 10^{-3} \mathrm{~Sm}^{2} \mathrm{~mol}^{-1}

x=3

Answer is 3

Posted by

Ritika Kankaria

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