IGNOU BCHCT 133 2026 - Arrange the following salt of magnesium in the order of increasing sol

Question

Arrange the following salt of magnesium in the order of increasing solubilities.
$MgF₂, MgCO₃, Mg₃(PO₄)₂$
[Given: $K_{sp}(MgF_2) = 3.7 \times 10^{-8}; K_{sp}(MgF_2) = 3.5 \times 10^{-8};$ and
$$K_{sp}(MgF_2) = 1.0 \times 10^{-25} \text{ at } 25 \text{ }^\circ\text{C}.]$ $

19 Jan 2026

Answer :

Word Count : 145

Let the molar solubility be (s). For ( \mathrm{MgF_2(s) \rightleftharpoons Mg^{2+} + 2F^-} ) [ K_{sp} = [\mathrm{Mg^{2+}}][\mathrm{F^-}]^2 = s(2s)^2 = 4s^3 ] [ s = \left(\frac{3.7 \times 10^{-8}}{4}\right)^{1/3} \approx (0.925 \times 10^{-8})^{1/3} ] [ s \approx 2.1 \times 10^{-3}\ \text{mol L}^{-1} ] --- For ( \mathrm{MgCO_3(s) \rightleftharpoons Mg^{2+} + CO_3^{2-}} )

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