Chapter 8: Q5 TY (page 168)
Find in equilibrium with 0.010MKCl saturated with.
Short Answer
The value of in equilibrium with 0.010M KCI saturated is
Chapter 8: Q5 TY (page 168)
Find in equilibrium with 0.010MKCl saturated with.
The value of in equilibrium with 0.010M KCI saturated is
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Systematic treatment of equilibrium for ion pairing. Let’s derive the fraction of ion pairing for the salt in Box , which are . Each case is somewhat different. All of the solutions will be near neutral pH because hydrolysis reactions of have small equilibrium constants. Therefore, we assume that and omit these species from the calculations. We work as an example and then you asked to work each of the others. The ion-pair equilibrium constant, comes from Appendix J.
Pertinent reaction:
Charge balance (omitting whose concentrations are both small in comparison with :
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Mass balance:
Only two of the three equations (B),(C) and (D) are independent. If you double (c) and subtract (D) , you will produce (B). we choose (C) and (D) as independent equations.
Equilibrium constant expression : Equation (A)
Count : 3 equations (A,C,D) and 3 unknowns
Solve: We will use Solver to find
unknown concentrations.
The spreadsheet shows the work. Formal concentration appears in cell . We estimate in cell and . The ionic strength in cell is given by the formula in cell . Excel must be set to allow for circular definitions as described on page role="math" localid="1655088766279" . The sizes of role="math" localid="1655088853561" are from Table and the size of is a guess. Activity coefficient are computed in columns . Mass balance appears in cell , and the sum of squares appears in cell . The charge balance is not used because it is not independentof the two mass balances.
Solver is invoked to minimizes in cell be varying in cells and . From the optimized concentration, the ion-pair fraction is computed in cell .
The problem: Create a spreadsheet like the one for to find the concentration, ionic strength, and ion pair fraction in . The ion pair formation constant from Appendix J is log for the reaction . The two mass balances are Estimate for input and then minimizes the sum of square of the two mass balances.
Calculate the ionic strength of (a) 0.008 7 M KOH and (b) 0.000 2 (assuming complete disassociation at this low concentration and no hydrolysis reaction to make ).
Findfor in 0.33mM.
What would be the charge balance if you add to the solution and it dissociates into?
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