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A saturated solution of #PbBr_2# is prepared by dissolving the solid salt in water. The concentration of #Pb_2^+# in solution is found to be 0.0115 M. What is the Ksp for #PbBr_2#?

Answer 1

Noah Aldrich

#K_(sp)=6.1xx10^-6#

We interrogate the solubility equilibrium.........

#PbBr_2(s) rightleftharpoonsPb^(2+) + 2Br^(-)#

Now #K_(sp)=[Pb^(2+)][Br^-]#.........And if we say that the solubility of #PbBr_2-=S#, then by stoichiometry........

#K_(sp)=[S][2S]^2=4S^3# (because #S=[Pb^(2+)]#, and #[Br^-]=2S#

#=4xx(0.0115)^3=6.1xx10^-6#.........

Can you define what is meant by a #"saturated solution......?"#

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Answer 2

Wyatt Atkins

[ \text{K}{\text{sp}} = [\text{Pb}^{2+}] [\text{Br}^-]^2 ] [ \text{K}{\text{sp}} = (0.0115)(2 \times 0.0115)^2 ] [ \text{K}_{\text{sp}} = 0.000322 ]

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.