Question:

The minimum volume of water required to dissolve 0.1 g lead (II) chloride to get a saturated solution (\(K_{sp}\) of \(\mathrm{PbCl_2} = 3.2 \times 10^{-8}\), atomic mass of Pb = 207 u) is :

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Find the solubility s from \(K_{sp} = 4s^3\) for \(\mathrm{PbCl_2}\), then divide the moles of 0.1 g salt by s to get the volume.
Updated On: Nov 11, 2026
  • 0.36 L
  • 17.98 L
  • 0.18 L
  • 1.798 L
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The Correct Option is C

Solution and Explanation

Molar mass of \(\mathrm{PbCl_2}\) = 207 + 2(35.5) = 278 g/mol.
Moles in 0.1 g = 0.1/278 = \(3.6 \times 10^{-4}\) mol.
\(\mathrm{PbCl_2 \rightleftharpoons Pb^{2+} + 2Cl^-}\), so \(K_{sp} = s(2s)^2 = 4s^3\).
\(s^3 = 3.2\times10^{-8}/4 = 8\times10^{-9}\), so \(s = 2\times10^{-3}\) mol/L.
Volume of water needed = moles/s = \(3.6\times10^{-4}/(2\times10^{-3}) \approx 0.18\) L.
Answer: (3) 0.18 L
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