Reference no: EM131281750

Problem 1 - Systematic Treatment of Equilibrium

Given the equilibrium reactions below and relevant constants, calculate the solubility of lithium fluoride at any pH. Plot p[Li⁺] vs. pH (minimum of 25 points on this plot). Ignore Activities.

LiF ? Li⁺ + F^-           K_sp = 1.7 x 10^-3

F^- + H₂O ? HF + OH^- K_b = 1.5 x 10^-11

LiF(s) LiF(aq)              K₁ = 0.591

H₂O ? H⁺ + OH^-           K_w = 1.0 x 10^-14

Problem 2 - Diprotic Weak Acids

In Harris, equation 10-19 (fractional dissociation of a weak acid in H2A form) was given. In a similar matter, demonstrate the derivation of equations 10-19, 10-20, and 10-21 (these equation numbers are from the 9th edition of Harris!) INCLUDING ACTIVITIES.

Problem 3 - Systematic Treatment of Equilibrium and Diprotic Weak Acids

Given the K_a values below, plot mole fraction of each possible carbonate species vs. pH (minimum of 25 points on this plot. It should look similar to the figure below for phosphate) for a solution of carbonic acid with a formal concentration of 0.100 M. Ignore the equilibrium of carbonic acid with CO₂ and Ignore Activities.

H₂CO₃ ? HCO₃^- + H⁺          K_a1 = 4.46 x 10^-7

HCO₃- ? CO₃^2- + H⁺         K_a2 = 4.69 x 10^-11

H₂O ? H⁺ + OH^-                  K_w = 1.0 x 10^-14

Problem 4 - Buffers

Using the pKa values in Appendix G and activity coefficients from Table 8-1, calculate the pH of each of the following buffer solutions (a) without activity and (b) with activity.

1. 0.025 M NaHCO₃ and 0.0030 M Na₂CO₃
2. 0.050 M NaHCO₃ and 0.015 M Na₂CO₃
3. 0.0050 M disodium hydrogen citrate and 0.050 M sodium dihydrogen citrate.
4. 0.050 M citric acid and 0.0050 M sodium dihydrogen citrate
5. 0.050 M NaF and 0.040 M HF

Problem 5 - Buffers

For each buffer system from problem #4, calculation the pH of the resultant solution when (a) 15.00 mL of 0.005000 M HCI are added, (b) 15.00 mL of 0.0400) M NaOH is added, and (c) 5.00 mL of 0.02500 M HCl and 8.00 mL of 0.03500 mL of NaOH are added. Assume a 100 mL sample of your buffer, made fresh for each part. Ignore Activities.

Problem 6 - Acid/Base Titration

Plot a titration curve of a 30.00 mL aliquot of 0.05000 M sodium hypochlorite with 0.07250 M HCl. Your plot should include a minimum of 10 points prior to the equivalence point and 10 points after the equivalence point.

Problem 7 - Diprotic Acid/Base Titration

Plot a titration curve of a 25.00 mL aliquot of 0.1000 M diprotic weak acid (pK₁ = 2.00, pK₂ = 6.50) with 0.05000 M NaOH. Your plot should include a minimum of 10 points in each variable range of the titration curve and both equivalence points. Do NOT calculate the Is' (acid only in solution) point (0.00 mL NaOH added). This plot has the same issue as the one in class.

Problem 8 - Acid/Base Titration

When titrating a weak, unknown base with HC1, you performed the following series of standardizations. Initially, you made a solution of approximately 0.1000 M NaOH and standardized this solution with KHP. You then diluted stock HCl to make a solution of approximately 0.1000 M. In an acid/base titration, you took a 25.00 mL aliquot of your HCI solution and titrated it vAh the standardized NaOH. Due to a bad day in lab, this standardization took more than 4 trials. Throw out any outliers. Finally, a pH titration was performed with a 25.00 mL aliquot of your unknown weak basenThis solution was made by dissolving 3.4581 grams of your unknown in 250.0 mL of water. Determine the pKb of your weak base (Don't worry about error in this value!). In addition; determine the molecular mass of the base and the error in this value. This error will be slightly flawed, you only did ONE titration of your unknoWics-o-illai your error will come from the standardizations. Data will be provided in an Excel file emailed from the Instructor after this exam has been assigned.

Attachment:- q.xlsx