g [McQuarrie 22-7] The value of Ksp for PbCrO4(s) in equilibrium with water at 25◦C is 2.8 · 10−13M2 . Write the chemical equation that represents the solubility equilibrium for PbCrO4(s) and calculate its solubility in grams per liter in water at 25◦C.

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Answer :

The solubility equilibrium reaction will be:

[tex]PbCrO_4\rightleftharpoons Pb^{2+}+CrO_4^{2-}M^2[/tex]

The  solubility in grams per liter in water at [tex]25^oC[/tex] is, [tex]1.7\times 10^{-4}g/L[/tex]

Explanation :

The solubility equilibrium reaction will be:

[tex]PbCrO_4\rightleftharpoons Pb^{2+}+CrO_4^{2-}M^2[/tex]

Let the solubility be 's'.

The expression for solubility constant for this reaction will be,

[tex]K_{sp}=[Pb^{2+}][CrO_4^{2-}][/tex]

[tex]K_{sp}=(s)\times (s)[/tex]

[tex]K_{sp}=s^2[/tex]

Given:

Solubility constant = [tex]K_{sp}[/tex] = [tex]2.8\times 10^{-13}[/tex]

Now put all the given values in the above expression, we get:

[tex]K_{sp}=s^2[/tex]

[tex]2.8\times 10^{-13}=s^2[/tex]

[tex]s=5.3\times 10^{-7}M=5.3\times 10^{-7}mol/L[/tex]

Now we have to convert the solubility in gram per liter.

Solubility = [tex](5.3\times 10^{-7}mol/L)\times \text{Molar mass of }PbCrO_4[/tex]

[tex]\text{Molar mass of }PbCrO_4=323.2g/mol[/tex]

Solubility = [tex](5.3\times 10^{-7}mol/L)\times 323.2g/mol[/tex]

Solubility = [tex]1.7\times 10^{-4}g/L[/tex]

Therefore, the solubility in grams per liter in water at [tex]25^oC[/tex] is, [tex]1.7\times 10^{-4}g/L[/tex]

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