Question

1. The concentration of Ag+ ion is a saturated aqueous solution of Ag2CrO4 was found potentiometrically equal to 1.56 x 10-4 M. Calculate the solubility in grams per liter and its solubility product. 2. The solubility product of a compound with a general formula M2X was found equal to 3.58 x 10-13 on the basis of solubility measurements and on the assumption that the ions formed are M7 and X-2. A more careful determination of the ionic species determined that the ionization products are M2+2 and X-2. Calculate the correct solubility product for M2X. 3. How many grams of NH4Cl should be added to 50 ml of 0.20 M NH3 solution in order to prevent precipitation of Mn(OH)2 when the solution is mixed with 50 ml of 0.020 M MnCl2?

Answer 1

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PART 1:

Dissociation is given by,

$Ag_{2}CrO_{4}_{(s)}\rightleftharpoons 2Ag_{(aq)}^{+}+CrO_{4}_{(aq)}^{2-}$

Given that, $[Ag^{+}]=1.56\times10^{-4}\;mol/L$

Hence solubility is given by, $S=1.56\times10^{-4}\;mol/L$

We know that 1 mole of Ag= 108 g.

Hence, Solubility is given by,

$S=1.56\times10^{-4}\;mol/L\times 108\;g/mol$

$\mathbf{\therefore S= 1.685\times10^{2}\;g/L}$

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Solubility product is given by,

$K_{sp}=\left [ Ag^{+} \right ]^{2}\times [CrO_{4}^{2-}]= \left [ 2\times 1.56\times10^{-4}\;mol/L \right ]^{2}\times\left [ 1.56\times10^{-4}\;mol/L \right ]$

$K_{sp}=\left [ Ag^{+} \right ]^{2}\times [CrO_{4}^{2-}]= \left [ 3.12\times10^{-4}\;mol/L \right ]^{2}\times\left [ 1.56\times10^{-4}\;mol/L \right ]$

$\mathbf{\therefore K_{sp}=1.519\times10^{-11}\;M^{3}}$