Consider the solubility of the sparingly-soluble salt Mn(OH)2. Write mass balanc
ID: 915793 • Letter: C
Question
Consider the solubility of the sparingly-soluble salt Mn(OH)2. Write mass balance and charge balance equations for dissolution of Mn(OH)2 in water. You only need to express concentrations of species relative to each other, do not worry about the absolute concentration..Assume only simple products of dissociation and ions normally expected in water; neglect any ion-pair formation. Using the solubility product constant and neglecting activity, find the pH and equilibrium concentration of Mn^2 and of OH in the saturated solution of Mn(OH)2 Now consider a solution of 0.1 M Ca(CIO04)} that is saturated with Mn(OH)2. Calculate the ionic strength of the Ca(C10,), solution (neglect any contribution of Mn(OH), to ionic strength). Including activities, find [Mn'*J and (OH J in the solution, and calculate the solution's pH. (It is convenient here to use pH = logA . = log(Kw/ AOH)Explanation / Answer
there are 4 questions in a single set.
we are not to bother about the absolute concentration as mentioned in the question
let "s " be the molar solubility of Mn(OH)2
Mn(OH)2 ----------> Mn+2 (aq) + 2 OH- (aq)
s 0 0
s 2s
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mass balance : MMn(OH)2 = M Mn+2 + 2 MOH-
Charge balance : MMn(OH)2 = 2M Mn+2 + MOH-
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b) The solubility product is not given in the question
so i am adding it from my side Ksp Mn(OH)2 = 2 x 10-13
Ksp = 4S3= 2 x 10-13
solving for s , we get s = 3.86 x10-5 = [Mn+2]
[OH] = 2s = 2 x 3.86 x10-5 = 7.72 x10-5
pH = 14 - pOH = 14 -4.12 = 9.88
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please post the remaining questions separately , i would be happy to help