Chapter 8: QDE (page 182)
Using activities, calculate the pH and concentration of in 0.050MLiBr at.
Short Answer
The pH of the given solution is 6.99
Chapter 8: QDE (page 182)
Using activities, calculate the pH and concentration of in 0.050MLiBr at.
The pH of the given solution is 6.99
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Get started for freeSystematic 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 :
role="math" localid="1655088043259"
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.
Interpolate in Table 8-1 to find the activity coefficient of when
Write the charge balance for an aqueous solution of arsenic acid, , in which the acid can disassociate to role="math" localid="1654936423245" . Look up the structure of arsenic acid in Appendix G and write the structure of
(a) Write the mass balance for in water if the species are and .
(b) Write the mass balance if the species are , and
(c) Write the charge balance for part (b).
Color Plate 4 shows how the color of the acid-base indicatorbromocresol green (H2BG) changes as NaCl is added to an aqueoussolution of (H1)(HBG2). Explain why the color changes from palegreen to pale blue as NaCl is added.
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