Determination of Ksp of Copper(II) Iodate by E.M.F. Measurement Essay Example for Free

Determination of Ksp of Copper(II) Iodate by E.M.F. Measurement EssayIntroductionCopper(II) iodate(V) ionizes weakly in waterCu(IO3)2 + aq Cu2+(aq) + 2IO3-(aq)For a saturated result of copper(II) iodate(V), concentration of IO3- ions doubles that of the Cu2+ (aq) ions, and Ksp of Cu(IO3)2(s) can be calculated by determining the concentration of Cu2+(aq) ion of a saturated Cu(IO3)2(aq).The e.m.f. of a galvanizing cell consisting of a Zn(s)/Zn2+(aq) half-cell and other half-cell containing a copper strip in contact with a saturated solution of Cu(IO3)2(aq) is measured by a commercial DMM. Concentration of Cu2+(aq) is determined with telephone extension to the EO taxs of the Zn(s)/Zn2+(aq) and the Cu(s)/Cu2+(aq) couples as well as the Nernst equation for a metal/metal ion half-cellwhere n is the number of electrons transferred in the reduction process.? Zn Zn2+ + 2e-Cu2+ + 2e- Cu ? n=2For the Zn(s)/Zn2+(aq) half-cell, = -0.76VFor the Cu(s)/Cu2+(aq) half-cell,Ecell = ER EL= (+ 0.34) + 0.0295 log Cu2+(aq) (-0.76)= (1.10) + 0.0295 log Cu2+(aq)When the voltage of the cell system is measured, the concentration of Cu2+ can be determined by the above equation. Therefore, the solubility product can be calculated by the above principle.PurposesTo determine the solubility product of copper(II) iodate(V) at room temperature and crush by e.m.f. measurement.Apparatus and Reagents employApparatus usedWell-platePlastic pipettesCopper wire electrodeZinc plate electrodeDigital multimeter (DMM)Connecting wires with crocodile clipsFilter paper strip, andSand paper1211121Reagents used1M ZnSO4(aq)0.3M KIO3(aq)0.15M CuSO4(aq), andSaturated KNO3(aq)Chemical Reactions InvolvedThe equation of dissolution of copper(II) iodate(V)Cu(IO3)2(s) + aq Cu2+(aq) + 2IO3-(aq)The equation of redox reaction between Zn and Cu2+Cu2+(aq) + Zn(s)Zn2+(aq) + Cu(s)Procedures1. 50 drops of 1M ZnSO4(aq) were placed into a well of the well-plate2. 25 drops of 0.3M KIO3(aq) were placed into an empty well next to the well containing the 1M ZnSO4(aq), by using a clean giant pipette3. The plastic pipette used in step(2) was cleaned. By using the same plastic pipette, 25 drops of 0.15M CuSO4(aq) were added and stirred well with a micro-stirrer or toothpick. 5 minutes were waited to attain equilibrium4. The two wells were connected by a strip of filter paper moistened with saturated KNO3(aq)5. A clean homemade copper wire electrode and a clean coat plate electrode were placed into the well containing the demented blue suspension and the well containing the 1M ZnSO4(aq) respectively6. The prepared galvanic cell was connected to a DMM. The steady voltage developed was recorded.ObservationsWhen the galvanic cell completed in step(5) was connected to the DMM, a steady voltage was developed. info and resultsTemperature of the aqueous solution = 26?E.m.f. of the cell formed by Zn(s)/Zn2+(aq, 1M) and Cu(s)/Cu(aq, saturated) = 0.997VDiscussions1. The expression of the Ksp of copper(II) iodate(V) = Cu2+(aq)eqm IO3-2eqm2. By the equation evaluated in the introduction,Ecell = (1.10) + 0.0295 log Cu2+(aq) = 0.997V0.0295 logCu2+(aq) = -0.103logCu2+(aq) = -3.492? Cu2+(aq)eqm = 3.225 10-3 moldm-3Concentration of Cu2+(aq) in the saturated pale blue suspension = 3.225 10-3 moldm-33. By the equation of dissolution of copper(II) iodate(V),Cu(IO3)2(s) + aq Cu2+(aq) + 2IO3-(aq)Cu2+(aq) IO3-(aq) = 1 2?IO3-(aq)eqm = 2 3.225 10-3 = 6.450 10-3 moldm-3Concentration of IO3-(aq) in the saturated pale blue suspension = 6.450 10-3 moldm-34. The value for Ksp of Cu(IO3)2= Cu2+(aq)eqm IO3-2eqm= (3.225 10-3) (6.450 10-3)2= 1.34 10-10 mol3dm-95. From the data of the Faculty of Chemistry and Technology, University of Split, the literature value of Ksp of Cu(IO3)2 is 6.94 10-8 mol3dm-9 1. Obviously, the literature value was much larger than the experimental value. The discrepancy came from several reasons1 The experimental temperature was 26?, which was different from the expect ed room temperature 25?. As temperature is the main factor of Ksp, the discrepancy of Ksp was caused by the difference of temperature2 The low quality of copper and zinc electrode may affected the e.m.f. taken from the DMM, so the Ksp result was also affected3 The concentration of solutions prepared may be different with the expected value. The e.m.f. given over out may not equal to the theoretical values, so the Ksp obtained may be different.ConclusionBy the e.m.f. method, the solubility product of copper(II) iodate(V) at room temperature and pressure was determined. Ksp for = 1.34 10-10 mol3dm-9Reference1 Solubility Product Constants, Faculty of Chemistry and Technology, University of Split http//www.ktf-split.hr/periodni/en/abc/kpt.html