Reference no: EM132508309

Analytical Chemistry

Complexometric and Precipitation Titration

Directions: Answer the ff. questions on a short white bond paper. For problem solving, write the systematic solution and box the final answer.

Question 1. Define the following:

a. Ligand

b. Chelate

c. Tetradentate chelating agent

d. Adsorption indicator

e. Argentometric titration

f. EDTA displacement titration

g. Water hardness

Question 2. Why are multidentate ligands preferable to unidentate ligands for complexometric titrations?

Question 3. Describe three general methods for performing EDTA titrations. What are the advantages of each.

Question 4. Why does the charge on the surface of precipitate particles change sign at the equivalence point of a titration?

Question 5. A solution was prepared by dissolving about 3.0 g of NaH₂Y₂·2H₂O in approximately 1 L of water and standardizing against 50.00-mL aliquots of 0.004423 M Mg²⁺. An average titration of 30.27 mL was required. Calculate the molar concentration of the EDTA.

Question 6. A solution contains 1.569 mg of CoSO₄(155.0 g/mol) per milliliter. Calculate

a. The volume of 0.007840 M EDTA needed to titrate a 25.00-mL aliquot of this solution.

b. The volume of 0.009275 M Zn²⁺needed to titrate the excess reagent after addition of 50.00 mL of 0.007840 M EDTA to a 25.00-mL aliquot of this solution.

c. The volume of 0.007840 M EDTA needed to titrate the Zn²⁺displaced by Co²⁺following addition of an unmeasured excess of ZnY^2-to a 25.00-mL aliquot of the CoSO4 solution. The reaction is

CO²⁺ + ZnY^2-à CoY^2- + Zn²⁺

Question 7. Calculate the volume of 0.0500 M EDTA needed to titrate

a. 29.13 mL of 0.0598 M Mg(NO₃)₂.

b. The Ca in 0.1598 g of CaCO3.

c. The Ca in a 0.4861-g mineral specimen that is 81.4% brushite, CaHPO₄·2H₂O (172.09g/mol).

d. The Mg in a 0.1795-g sample of the mineral hydromagnesite, 3MgCO₃Mg(OH)₂·3H₂O (365.3 g/mol).

e. The Ca and Mg in a 0.1612-g sample that is 92.5% dolomite, CaCO₃.MgCO₃(184.4 g/mol).

Question 8. Calculate the pCrO₄ in a solution formed by mixing 50.0 mL 0.50 M K₂CrO₄ with 50 mL 0.50 M AgNO₃.(Ksp = 1.1x10^-12)

Question 9. Calculate the pCrO₄ in a solution formed by mixing 50.0 mL 0.50 M K₂CrO₄ with 125 Ml 0.50 M AgNO₃.(Ksp = 1.1x10^-12)

Question 10. Calculate the pAgin a solution formed by mixing 20.0 mL 0.50 M Na₃PO_4,20 mL 1.20 M AgNO₃ and 20 mL H₂O. (Ksp = 1.3 x 10^-20)

Question 11. A 0.970 g sample containing KCN and inert materials was dissolved in water for Liebig titration. Concentrated NH₃ and NaI were added to the solution for enhanced end point detection. The solution required 40.1 mL 0.101 M AgNO₃ to reach the turbid end-point. Find the %KCN in the sample.