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- (10 points) A mixture is made of two weak bases. A 15.00 mL aliquot of the base mixture is analyzed by titration with a 0.140 M strong acid. The resulting titration data is plotted in the graph below. Use this graph to determine the answers to the questions in the table below.
Numerical answers do not need to be perfectly accurate, but they should be reasonable.
Is there more of the weaker base, or the stronger base, in the mixture?
Approximately how much titrant (in mL) was needed to titrate only the the weaker base?
What is the concentration of the stronger of the bases in the mixture?
What is the approximate pKa of the stronger base?
What is the approximate pKa of the weaker base?
Titrant volume added (mL)
- (15 points) A 25.00 mL aliquot of a solution containing 40.00 mM phosphoric acid is titrated with a 0.200 M LiOH titrant. Determine the pH of the solution during the course of the titration at the volumes indicated in the table to the right.
Titrant volume added (mL)
Cell Potential (V)
3) (12 points) A 30.00 mL solution containing 45.00 mM iodine and buffered to pH 8.94 is titrated with a solution of Pb4+. The concentration of lead(IV) in the titrant is 75.00 mM. The cell potential is monitored with a platinum wire cathode, and a S.C.E. (0.241 V) anode as the reference electrode. Determine what potential will be measured for each of the titration volumes listed in the table to the right.
Use the half reactions below to determine the cell potentials.
Pb4+ + 2e– ⇌ Pb2+ E° = 1.69 V
IO3– + 3H2O + 6e– ⇌ I– + 6OH– E° = 0.269 V
- (6 points) A 50.00 mL solution containing 5.00 mM each of Ag+ and Co3+ buffered at pH 9.00 is mixed with 50.00 mL of 12.50 mM EDTA. What will be the concentration of the metals, and EDTA that are not part of a complex?
See page 7 for EDTA constant tables
- (7 points) A 20.00 mL solution containing 50.00 mM AgNO3 and 100.00 mM Pb(NO3)2 is titrated by precipitation with 250.0 mM KCl titrant. Determine the concentrations of the metals (Ag+ and Pb2+) free in solution at the given titration volumes.
1.8 # 10“4
1.7 # 10“5
Solubility Table pKsp Ksp
Chlorides: L ! Cl“
CuL 6.73 1.9 # 10“7
AgL 9.74 1.8 # 10“10
Hg2L2 17.91 1.2 # 10“18