Electrochemistry experimen Essay

Introduction Redox answers be reactions where the oxidization states of the atoms variety show. The atoms are either oxidized or reduced, depending if they lose or hold electrons. Electrochemical cells are devices that cause a current from redox reactions. It is set up so that electrons lost from one of the reagents potentiometer travel to another reagent. This creates a voltage, which is similarly known as the electric capablenessityity difference. This voltage can be register if a high- metro voltmeter or multimeter is connected to the roundab come in. sodium chloride duet is used to entirelyow migration of ions amongst two electric cells to maintain disinterest of declarations. It is usually made up of a filter paper moistened with an inert resultant role or an inert outcome/ gel salt bridge to prevent oxidisation of certain ions. This s antiophthalmic factorle is divided into 2 several(prenominal)ises part A and part B. Part A Objective To canvass the ef fect of transfigure in lead(II) ion submerging on the potential of the Pb2+(aq) Pb(s) electrode Introduction This experiment investigates the e. m. f. of the cell Cu(s) Cu2+(aq) Pb2+(aq)Pb(s).Keeping the ion parsimony in the grunter electrode waits eonian(1M) and varying the ion dousing in the lead electrode system, the effect of change in lead(II) ion concentration on the potential of electrode as well as the Kc of the above reaction can be found. Chemicals Copper intersect x1, lead foil x1, 1M Cu2+ rootage, 0. 1M Pb2+ firmness, saturated potassium treat solution tool 250 cm3 beakers, 50cm3 beakers multimeter, distilled water bottle, filter papers, galvanic wires with electrode holders, forceps, 100ml volumetric flask,10ml pipette x2, dropper process 1. The 0. 1M, 0.01M, 0. 001M, 0. 0001M Pb2+ solutions were prepared from 0. 1M Pb2+ solution by dilution(1 share solution plus 10 portions water). 2. The copper and lead electrodes were cleaned with a lynchpin paper. 3. The circuit was connected as the draw below. 4. The e. m. f. was record when the data shown was stable. 5. The above stairs(2-4) were repeated with 0. 01M, 0. 001M and 0. 0001M Pb2+ solutions. rubber precaution Potassium nitrate solution Contact with combustible material whitethorn lead to fire 1M Copper(II) sulphate solution wounding and irritating to eyes and skin. > guard duty goggles should be worn.Experimental set-up Results Pb2+/M logPb2+ E/V 0. 1 -1 0. 482 0. 01 -2 0. 502 0. 001 -3 0. 521 0. 0001 -4 0. 545 interpret of E against log Pb2+ Trend shown minded(p) the ion concentration in the copper electrode system constant, it is found that the potential of the cell drops as the lead(II) ion concentration increase. The electrode potential is inversely comparative to the ten folds of ion concentrations. computer science When the reaction Cu2+(aq) + Pb(s) > Pb2+(aq) + Cu(s) achieves equilibrium, the last(a) e. m. f. of the cell=0 volt. The equilibrium sort of this re action isKc= Pb2+(aq) Cu(s) /Cu2+(aq) Pb(s) The effective concentration of Pb(s)/ Cu(s) are independent of its amount inclose and can be considered as constant. This reduces the typeface to Kc= Pb2+(aq) /Cu2+(aq) = 11021 evidence The potential of the cell decreases ad the ion concentration of Pb2+ increases. come along Analysis Using the Nernst equation E=E? -0. 059/n logox/red, Take Pb2+=0. 1 M as an example, E=0. 47-0. 059/2 log(0. 1/1)=0. 4405(V) Pb2+/M logPb2+ E/V(calculated) E/V( careful) %difference 0. 1 -1 0. 4405 0. 482 9. 42% 0. 01 -2 0. 529 0. 502 5. 10%.0. 001 -3 0. 5585 0. 521 6. 71% 0. 0001 -4 0. 588 0. 545 7. 31% It is shown that difference is break mingled with the calculated value and measured value.This may be because of different conditions, resistance of the multimeter or errors in preparation of unlike concentrations of solutions. Part B Objective To chance on out the equilibrium constant by e. m. f. measuring rod Introduction The equilibrium constant for the below reaction is found out Ag+(aq) + Fe2+(aq) Fe3+ (aq) + Ag(s) By e. m. f. measurement on the cell Pt Fe2+(aq), Fe3+(aq)Ag+(aq)Ag(s) Chemicals 0. 1 M Fe3+ solution, 0.2 M iron(II)sulphate, 0. 2M atomic number 56 nitrate, 0. 4M silver nitrate, platinum electrode, silver electrode Apparatus jelly salt bridge, 250 cm3 beakers, 50cm3 beakers ,multimeter, distilled water bottle, electric wires with electrode holders, forceps, 10ml pipette x2 Procedure 1. Equal volumes of 0. 2M FeSO4 and 0. 2M Ba(NO3)2 were entangled and the precipitate was allowed to settle without disturbance. 2. Equal volumes of 0. 1M iron(II) nitrate solution obtained and the iron(III)nitrate solution were mixed. This was the Fe2+(aq)/Fe2+(aq) half-cell. 3.The 0. 4M, 0. 2M, 0. 1M, 0. 05M, 0.025M silver nitrate solutions were prepared from 0. 4M silver nitrate solution by dilution. 4. The silver electrode was cleaned with a sand paper. 5. The circuit was connected as the diagram below. 6. The e. m. f. was recorded when the data shown was stable. 7. The above steps (4-6) were repeated with 0. 2M, 0. 1M, 0. 05M, 0. 025M silver nitrate solutions. sentry go Precaution Silver nitrate harmful and oxidizing 1) Poisonous if swallowed or inhaled 2) Skin concussion with silver nitrate solid or solutions is likely to leave silver stains on the skin. Barium nitrate is poisonous and precise harmful if swallowed.It is also a steady oxidizer, so may be dangerous if mixed with flammable materials. Experimental Set-upResults Ag+/M logAg+ E/V 0. 4 -0. 398 0. 023 0. 2 -0. 699 0. 005 0. 1 -1 -0. 030 0. 05 -1. 301 -0. 050 0. 025 -0. 025 -0. 053 Graph of E against logAg+(aq) Calculation When the reaction reaches equilibrium, two forward and disinclined reactions proceed to the equivalent extent. This means that both the half cell reactions would have the same potential to proceed, so that the net e. m. f of the cell =0 volt at equilibrium.From the graph, the x-intercept is logAg+(aq)=-0.72, hence ,Ag+(aq)eqm=0. 1905 Ag+(aq) + Fe2+(aq) Fe3+ (aq) + Ag(s) KC= Fe3+ (aq)/ Ag+(aq) Fe2+(aq) =0. 1/ (0. 1905X0. 1) =5. 2493(mol2dm-6) 5. 25(mol2dm-6) Conclusion The equilibrium constant for the reaction between Fe2+/Fe3+ and Ag+ is 5. 25 mol2dm-6. Discussion(for both parts) 1. realistic Errors -The electrodes (Cu(s),Pb(s),Ag(s)) were not cleaned real well with a sand paper so that they are not conducting electricity in all parts. The e. m. f. measured may hence be underestimated. -The same ammonium nitrate/gelatine salt bridge was used several times in part II of experiment.Ions of previous measurement may remain in the salt bridge and change the concentration of ions in the next measurement. -The instrument including pipettes, beakers and volumetric flask may not be washed to be very clean. The error in concentration may be enormous when handling very dilute solutions (e. g. 0. 001M, 0. 0001M, 0. 025M) -The electrode touched the salt bridge once so that the accuracy of measurement of e. m. f. was affected. The solution is not exactly passed. -Air faulting may be present in the ammonium nitrate/ gelatine salt bridge, increasing the resistance of ion migration. 2.Difference in effect of ion concentration on electrical potential of cell -In part A, the cell e. m. f. increases as Pb2+(aq) decreases. However, in part B, the e. m. f. drops as Ag+(aq). This suggests that when the species is a stronger oxidizing agent in the reaction and undergoes reduction, the presence of its ions tends to increase the e. m. f. whereas the one which undergoes oxidation tends to reduce the e. m. f. The species with more supportive amount reduction potential has a positive effect but the one with little positive potential has a prejudicial effect.Reference Physical Chemistry II by TM Leung and CC Lee( p. 295-298 &299-301).