# Guia de analitica

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• Publicado : 30 de noviembre de 2010

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he following problems are intended as a study guide for the Midterm.
1) Calculate the concentrations of Ag+, CN-, and HCN in a saturated solution of AgCN whose pH is buffered at 9.00:
AgCN(s) Ag+ +CN- Ksp = 2.2 x 10-16
CN- + H2O HCN + OH- Kb = 1.6 x 10-5
Assume that the ionic strength is fixed at 0.10 M by addition of an inert salt. The hydrated radius are 0.75 pm, 0.755 pm for Ag+ and CN-respectively.
2) Consider the following equilibrium:
PbO(s) + H2O Pb2+ + 2OH- Ksp = 2.2 x 10-16
Pb2+ + 2H2O PbOH+ + H3O+ Kb = 1.6 x 10-5
How many grams of PbO will dissolve in a 1.00 L solution ifthe pH is fixed at 10.50?
3) An iodate/iodide cell consists in the following reactions:
2IO3- + I- + 12H+ + 10 e- I3- + 6H2O E°= 1.210 V
I3- + 2e- 3I- E°= 0.535 V
If the solution in the cellcontains 0.010 M of IO3-, 0.010 M of I-, 1x10-4 of I3-, and a pH buffered at 6.00, A) Calculate the equilibrium constant (K) for the reaction. B) At what pH would the concentrations of IO3-, I-, and I3-listed above reach equilibrium?
4) Consider the cell
Pt(s)|H2(g, 0.100 bar)|H+(aq, pH = 2.54)||Cl-(aq, 0.200 M)|Hg2Cl2(s)|Hg(l)|Pt(s)
Find the potential of the cell and state whether the reaction isspontaneous. (1 bar = 0.987 atm)
CHEM210 : Spring 2010 [STUDY GUIDE FOR MIDTERM 1]
5) 30.0 mL of EDTA 0.040 M was added to 25.0 mL of a Ni2+ solution. Upon addition of 6 drops of calgamiteindicator, the solution turned blue. The solution was then titrated with 0.018 M of Zn2+. After the addition of 16.1 mL, the solution turned purple. What is the concentration of Ni2+ in the unknown solution?6) 100.00 mL of buffer solution is made by adding 0.120 mol of C6H5COOH and 0.120 mol of C6H5COONa (with a Ka = 6.28 x 10-5). Calculate the pH of the solution after adding 60 mL of a NaOH 0.1 Msolution.
7) A KMnO4 solution that was standardized with an oxalate solution. The oxalate solution was prepared by dissolving 0.3562 g of Na2C2O2 (MW=130.00) in 1.0 M of H2SO4 in a 250.00 mL volumetric...