Equal volumes of (aq) and (aq) are mixed at

CHEMISTRY · Single correct · AP · Chemistry · Equilibrium · Equilibrium

Problem

Equal volumes of 0.010 M0.010\,\text{M} MgCl2\text{MgCl}_2(aq) and 0.010 M0.010\,\text{M} NaF\text{NaF}(aq) are mixed at 25 ∘C25\,^{\circ}\text{C}. The solubility product constants are Ksp(MgF2)=6.4×10−9K_{sp}(\text{MgF}_2)=6.4\times10^{-9} and Ksp(Mg(OH)2)=1.8×10−11K_{sp}(\text{Mg(OH)}_2)=1.8\times10^{-11}. Assuming activities equal concentrations and no side reactions other than possible precipitation, which statement is most consistent with the outcome? (a) No precipitate forms because most fluoride salts are highly soluble according to solubility rules. (b) Mg(OH)2\text{Mg(OH)}_2 precipitates because it has the smaller KspK_{sp} value and is therefore the least soluble compound. (c) MgF2\text{MgF}_2 precipitates because the ion product [Mg2+][F−]2[\text{Mg}^{2+}][\text{F}^-]^2 exceeds KspK_{sp}. (d) No precipitate forms because, after dilution, the ion product for MgF2\text{MgF}_2 is still below its KspK_{sp}.

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