AP Chemistry - OAK PARK USD



Chemistry 7: ElectrochemistryName __________________________A.Balancing Redox Equations (20.2)assign oxidation to each atomdetermine oxidized atom (oxidation # increases) and reduced atom (oxidation # decreases)split into oxidation and reduction half-reactionseliminate spectator ions (ion that doesn't contain atom that changes oxidation number—often cation) balance each half reactionbalance atoms except O and Hbalance O, by adding H2Obalance H, by adding H+balance charge, by adding e-multiply half-reactions to equalize electronsadd half-reactions togethersimplify by reducing H2O and H+ and/or coefficientsthis process assumes reaction takes place in acid (H+), if in base, add an OH- for each H+ in the final equation (combine H+ and OH- to make water)B.Standard Reduction Potentials Chart (20.4 to 20.6)1.reduction half reactions a.listed from “greatest” electron affinity to “least”b.2 H+ + 2 e- ? H2: Eored = Eoox = 0 Vc.Eo measured in volts, 1 V = 1 J/C1."o": standard conditions (25oC, 1 atm, 1 M) 2.not proportional to amount of chemical d.oxidation is reverse (Eoox = -Eored)2. Eo = Eored + Eooxa. Eo > 0 is a spontaneous reaction(reduction listed above oxidation on chart)b.voltage under nonstandard conditions1.Nernst equation: E = Eo – (RTo/nF)lnQR (8.31), To (298) and F (96,500) are constant(E = Eo – (0.0257/n)lnQ)2.Q (quotient) = Product/Reactantsa.partial pressure (atm) gases, concentration (M) of ionsb.solids and liquids excludedC.Voltaic (Galvanic) Cell (20.3)spontaneous redox reaction generates voltage ? electrons flow through wires from oxidation cell to reduction cell anode (–)Voltage > 0cathode (+)salt bridgeporous membranesite of oxidationsite of reduction1.oxidation half cell (– anode)a.reducing agent gives up electrons to external circuit (wires) b.anions flow toward anode through salt bridge/ porous membrane to maintain electrical neutrality2.reduction half cell (+ cathode)a.oxidizing agent attract electrons from wire b.cations flow toward cathode through salt bridge3.predict how change affects voltagea.reactant: ?[ions] or ?Pgases ? ?E (voltage)b.over time: ?reactant & ?product ? ?Ec.size of electrode and chamber: no changed.remove salt bridge: E = 0D.Electrolytic Cell (20.9)battery forces non-spontaneous redox reaction by pulling electrons from reducing agent and sending to oxidizing agentanode (+)+ Battery –cathode (–)site of oxidationsite of reduction1.Eo < 0 (battery makes up for deficit)2. oxidation at + anode, reduction at – cathode3. electrolysis in water solutions (inert electrodes)a. cathode reduction: H2O or cation (greater Eored)1. columns 1, 2 or Al3+: 2 H2O + 2 e- ? H2 + 2 OH-2.acid (H+): 2 H+ + 2 e- ? H23. otherwise: Mx+ + X e- ? Mb. anode oxidation: anion or H2O1.Cl-, Br-, I-: 2 X- ? X2 + 2 e-2.base (OH-): 4 OH- ? O2 + 2 H2O + 4 e-3. otherwise: 2 H2O ? O2 + 4 H+ + 4 e- 4.electroplating (transition metal cations coat cathode)a.current, I, measured in amperes (amps—A)1 A = 1 C/s (coulomb/second)b.mass plated given current, I, and time, t(t) s x (I) C x mol e- x mol Mx+ x (MM) g = __ g 1 s 96,500 C X mol e- 1 mol Mx+c.time for plating—calculate right to leftExperiments1.Voltaic Cell Lab—Measure the voltage of six voltaic cells, determine the reduction half-cell potential for each metal and compare these results to the standard values. Polish the metal electrodes (1-Ag, 2-Cu, 3-Pb, and 4-Zn). Half fill each quadrant of the Petri dish with the 0.1 M nitrate salt of the corresponding metal. Drape the KNO3-soaked ring so that it is submerged in each quadrant. Measure the voltage of each system (reverse the electrodes when V < 0). Record the metal that is connected to the black electrode (oxidation) and the voltage (Elab) for the overall reaction.plete the chart for each voltaic cell.Ag and CuAg and PbAg and ZnBlackElabBlackElabBlackElabCu and PbCu and ZnPb and ZnBlackElabBlackElabBlackElabb.Determine the standard voltage (Eolab) for each cell.Half ReactionAg + CuReductionOxidationOverallEolabAg + PbReductionOxidationOverallEolabAg + ZnReductionOxidationOverallEolabc.Determine the lab values for Eored for Cu, Pb and Zn given Eored for Ag is 0.80. CellEored = 0.80 – EolabEotable% ?Ag + CuAg + PbAg + pare the voltages of the remaining systems with the table values. (There is no need to correct for 0.1 M)CellEolabEotable = Eored + Eoox% ?Cu + PbCu + ZnPb + Zn2.Electrolysis Lab—Part 1: Observe the electrolysis of KI(aq).Fill a weighing boat with 0.5 M KI. Add 3 drops indicator. With the power supply OFF, attach a piece of graphite to each wire lead and then plug in the power supply into the electric outlet. Dip the two pieces of graphite into opposite sides of the weighing boat for 10 seconds. Observe changes at the cathode (black electrode) and anode (red electrode), record the observations. Turn off the power supply and remove the graphite.a.(1) What color change occurs at the cathode?(2)Given that pink indicates the presence of OH-, write the half-reaction that occurs at the cathode.b.(1)What color change occurs at the anode?(2)Given that amber indicates the presence of I2, write the half-reaction that occurs at the anode.c.Are these reactions consistent with the predicted reactions based on KI as the electrolyte? ExplainPart 2: Measure the change in mass of the zinc electrode and the volume of hydrogen gas produced during electrolysis, calculate the molar mass of zinc and compare the value to the periodic table.Fill a 150 mL beaker ? full with conducting solution. Fill the 25 mL volumetric flask with the conducting solution from the beaker. Place rubber dam over the mouth of the flask, invert it and place it in the beaker (mouth down). Scrap off the rubber dam and slip the J-shaped electrode inside the flask without getting any air in. Polish the zinc and mass it (m1). Connect the wire lead attached to the black side of the power supply to the J-electrode (cathode). Connect the wire lead attached to the red side of the power supply to the zinc (anode). Turn on the power supply. Hydrogen gas should be bubbling from the J-electrode. Record the start time (t1). When the water level in the flask is near the 25 mL line, carefully raise the flask so that the level of the conducing fluid solution inside the flask is the same as the level in the beaker. When the water line in the flask is at 25 mL, turn the power supply off and disconnect the wires from the zinc and J-electrode. Record the stop time (t2). Return the conducting solution to the stock bottle. Scrub the zinc with a scrub pad under running water. Thoroughly dry the zinc and then mass it (m2). Record the temperature (T), lab pressure (Plab) and water vapor pressure (PH2O).d.Record the data.m1t1m2t2VTPlabPH2O25.0 plete and balance the redox reaction between zinc metal and water. Reduction Oxidation Overallf.Calculate the molar mass of Zn by completing the chart.Mass of Zinc lostVolume in LPressure in atmTemperature in KMoles of H2Molar Mass of Zinc% ? g.Why is it necessary to equalize the water level inside the volumetric flask with the water level in the beaker?h.Calculate the average current during the electrolysis by completing the chart.Total charge Q in CTotal time T in sCurrent I (I = Q/t)i.Calculate the approximate voltage needed to perform the electrolysis. (Assume standard conditions) Practice ProblemsA.Oxidation-Reduction Reactions1.Balance the redox equation in acid. MnO4- + NO2- + H+ ? Mn2+ + NO3- + H2O2.Balanced the redox equation in baseCr(OH)3(s) + ClO- ? Cl- + CrO42-3.Balance the redox equation in acid: Zn(s) + NO3- ? Zn2+ + NH4+.4.Balanced the redox equation in base: NO2- + Al(s) ? NH3(aq) + Al(OH)4-5.Balance the disproportionation reaction (same element undergoes oxidation and reduction): Cl2(g) ? Cl- + ClO-.inacidinbase6.Balance the reaction: P4(s) ? H2PO2- + PH3(g) inacidinbase7.Write net ionic equations for the following redox reactions.a.Solid iron + iron(III) sulfateb.Potassium dichromate + acidified hydrogen peroxide.8.The mass percent of H2O2 in a hydrogen peroxide solution is determined by titration with an acidified solution of KMnO4.a.Balance the redox reaction: MnO4- + H2O2 + H+ ? Mn2+ + O2 + H2O.oxidation reduction overall b.How many moles of MnO4- are needed to react all the H2O2 if 2.647 mL of 0.0200 M KMnO4 is added?c.How many moles of H2O2 reacted with the MnO4-?d.How many grams of H2O2 reacted with the MnO4-? e.What is the % H2O2 if 0.150 g of solution is used?B.Standard Reduction Potentials Chart9.Consider the Standard Reduction Potential Chart.a.What are the standard conditions?Highlight the correct option.b.When comparing two reactants (on the left side of the chart), the reactant that is listed (higher/lower) on the chart is the stronger oxidizing agent.c.When comparing two products (on the right side of the chart), the product that is listed (higher/lower) on the chart is the stronger reducing agent.d.The strongest reducing agents are found in column (1/17) on the periodic table. e.The strongest oxidizing agents are found in column (1/17) on the periodic table. f.Reactive (metals/nonmetals) tend to lose electrons and act as good (oxidizing/reducing) agents.g.When combining two half reactions, the left side agent listed higher on the chart will (give/receive) electrons from the right side agent listed lower on the chart.h.Write the equations for each half-reaction and overall reaction. Calculate Eo. Balanced reactionEoZn ? Zn2+Br2 ? Br-OverallH2 ? H+Ag+ ? AgOveralli.A spontaneous reaction has a (positive/negative) Eotot.j.Is the redox reaction, Cu(s) + Cl2(g) ? CuCl2(s), spontaneous? Support your answer with calculations. 10.Indicate where on the Standard Reduction Potentials Chart you would find:a.The chemical species that is the easiest to oxidize.b.The chemical species that is the easiest to reduce.11.Using standard reduction potentials, calculate the standard voltage for each of the following reactions.Cl2(g) + 2 I - ? 2 Cl- + I 2(s)Ni(s) + 2 Fe3+ ? Ni2+ + Fe2+Fe(s) + 2 Fe3+ ? 2 Fe2+2 Al3+ + 3 Ca(s) ? 2 Al(s) + 3 Ca2+12.Using standard reduction potentials, highlight the stronger reducing agents for each of the following pairs.Fe(s) or Mg(s)Ca(s) or Al(s)H2(g) or H2S(g)Sn2+ or Fe2+13.The unbalanced reduction half-reactions that operate in a car battery follow.PbSO4(s) ? Pb(s) + SO42- Eored = -0.356 VPbO2(s) + SO42-? PbSO4(s) Eored = 1.687 Va.Write balanced half reactions and the overall reaction. Label which reaction occurs at the anode and cathode.b.Calculate Eotot for the cell.c.Write the Nernst equation for the overall reaction.d.Calculate the voltage when [H+] = 2.0 x 10-4 M and [SO42-] = 0.50 M.e.What would happen to the voltage of the battery if the concentration of [H+] increased justify your answer)?C.Voltaic (Galvanic) Cell14.Answer the following questions based on the diagram.a.whichZnZn2+CuCu2+species is reduced?species is oxidized?species gives up its electron?species accepts electrons?ion passes through salt bridge?reducing agent?oxidizing agent?electrode is the cathode?electrode is the anode?oxidation half cellreduction half cellb.What memory device can be used to remember that the cathode is the site of reduction and + ions pass through the porous membrane to the cathode?plete the voltaic cell drawing using the half-reactions.Ni2+ + 2 e- ? Ni(s)Eored = -0.25 VFe2+ + 2 e- ? Fe(s)Eored = -0.44 VLabel the anode metal, cathode metal, site of oxidation, site of reduction, cation flow, anion flow, voltage, oxidation half-reaction, reduction half-reaction, and overall reaction.(You will need to figure out which reaction occurs at the anode, which at the cathode, and what the voltmeter would read under standard conditions. Assume each metal electrode is immersed in 1 M nitrate salt of the metal.)e- ?Voltage =e- ?oxidation half reactionreduction half reactionoverall reaction16.For the generic reaction: A + B ? A- + B+, for which Eo is a positive number, answer the following questions:a.What is being oxidized, and what is being reduced?b.If you made a voltaic cell out of this, what half-reaction would be occurring at the cathode, and what half-reaction would be occurring at the anode?c.Which half-reaction from (b) is higher on the Standard Reduction Potential Chart?17.A voltaic cell consists of a strip of aluminum in a solution of Al(NO3)3 in one beaker, and in the other beaker a strip of nickel in a solution of Ni(NO3)2. The overall reaction is:2 Al(s) + 3 Ni2+ ? 2 Al3+ + 3 Ni(s)a.What is being oxidized, and what is being reduced?b.Write the half-reactions that occur in the beakers. (Indicate which reaction takes place at the anode and which takes place at the cathode.)c.Indicate the signs of the two electrodes.d.Do electrons flow from the aluminum to the nickel or from the nickel to the aluminum?e.In which directions do the cations migrate and in which direction do the anions migrate through the solution?18.A voltaic cell consists of a strip of lead metal in a solution of Pb(NO3)2 in one beaker, and in the other beaker a platinum electrode is immersed in a NaCl solution, with Cl2 gas bubbled around the electrode. The two beakers are connected with a salt bridge.a.Write the equation for the overall cell reaction.b.What is the overall voltage generated by the cell under standard conditions?c.Which electrode serves as the anode, and which serves as the cathode?d.Does the Pb electrode gain or lose mass as the cell reaction proceeds?D.Electrolytic Cell19.Answer the following questions based on the electrolysis of fused (melted) sodium chloride.a.whichCl2Cl-NaNa+species is reduced?species is oxidized?species gives up its electron?species accepts electrons?species has a higher electron affinity?species is the reducing agent?species is the oxidizing agent?b.Write the equations for the electrolysis of NaCl.oxidation half reactionreduction half reactionoverall reactionc.What mass of Na(l) is produced using a current of 3.00 A for one hour? 20.Which cell...ElectrolyticVoltaica.has a battery?b.has a salt bridge?c.is spontaneous?d.has a positive anode?21.Write equations for the oxidation, reduction and overall reactions for the electrolysis of the salt solutions.NaClCuSO4Ba(OH)2HNO3Na2CO3KF22.An electrolytic cell contains a solution of Cr(NO3)3. a.Write the anode, cathode and overall equations.anode cathode overall b.How long will it take to deposit 15.0 g of chromium metal, using a current of 4.50 A?c.A current of 4.50 A for 30.0 minutes passed through the cell. The initial electrolyte contained 250 mL of 1.00 M Cr(NO3)3. Determine the(1)Initial moles of Cr3+.(2)moles of Cr3+ reacted.(3)Concentration of Cr3+ after 30.0 min. of electrolysis.(4)Concentration of H+ after 30.0 min. of electrolysis.(5)Mass of Cr(s) that plate out at the cathode.Practice Multiple ChoiceBriefly explain why the answer is correct in the space provided.1.H2Se + 4 O2F2 ? SeF6 + 2 HF + 4 O2Which is true regarding the reaction represented above? (A)Oxidation number of O does not change. (B)Oxidation number of H changes from -1 to +1.(C)Oxidation number of F changes from +1 to -1. (D)Oxidation number of Se changes from -2 to +6.2.6 I- + 2 MnO4- + 4 H2O ? 3 I2 + 2 MnO2 + OH-Which statement regarding the reaction is correct?(A)Iodide ion is oxidized by hydroxide ion.(B)MnO4- is oxidized by iodide ion. (C)Manganese oxidation number changes from +7 to +2.(D)Oxidation number of iodine changes from -1 to 0.3. 2 H2O + 4 MnO4- + 3 CIO2- ? 4 MnO2 + 3 CIO4- + 4 OH- Which species acts as an oxidizing agent in the reaction? (A)MnO4-(B)CIO4-(C)CIO2-(D)MnO24.Which species CANNOT function as an oxidizing agent?(A) Cr2O72-(B) MnO4-(C) NO3-(D) I-5.When acidified solutions of K2Cr2O7 and Na2S are mixed, Cr3+ and S are formed. Which is the best reducing agent?(A) K2Cr2O7(B) Na2S(C) Cr3+(D) S6. _Ag+ + _AsH3 + _OH- ? _Ag + _H3AsO3 + _H2O What is the coefficient for OH- in the balanced equation? (A)2(B)4(C)5(D)67._Cr2O72- + _e- + _H+ ? _Cr3+ + _H2OWhat is the coefficient for H+ in the balanced half-reaction?(A) 2(B) 6(C) 7(D) 148._Mg + _NO3– + _H+ ? _Mg2+ + _NH4+ + _H2OWhat is the coefficient for H+ in the balanced equation?(A) 1(B) 3(C) 5(D) 109._CrO2– + _OH– ? _CrO42– + _H2O + _e–What is the ratio of the coefficients OH–/CrO2– in the balanced half-reaction(A) 1:1(B) 2:1(C) 3:1(D) 4:110._Fe(OH)2 + _O2 + _H2O ? _Fe(OH)3 If 1 mole of O2 oxidizes Fe(OH)2, how many moles of Fe(OH)3 can be formed? (A)2(B)3(C)4(D)511.In which species does sulfur have the same oxidation number as it does in H2SO4? (A)H2SO3 (B)S2O32- (C)S2- (D)SO2Cl2 12.2 HClO + 3 O2 ? 2 HClO4As the reaction proceeds to the right, the oxidation number of chlorine changes from(A)-1 to +3(B)-1 to +5(C)+1 to +7(D)+3 to +713. Which will generate H2(g) when added to 1 M HCl?(A) CuS (B) Zn (C) CaCO3 (D)Mg(OH)14. _Cr2O72- + _H2S + _H+ ? _Cr3+ + _S + _H2OWhat is the coefficient for H+ in the balanced equation? (A)2(B)4(C)6(D)815. 3 Cu + 8 H+ + 2 NO3- ? 3 Cu2+ + 2 NO + 4 H2OWhich statements about the reaction are true? I. Cu acts as an oxidizing agent. II. Nitrogen's oxidation state changes from +5 to +2.III. Hydrogen ions are oxidized to form H2O. (A)I only (B)II only(C)III only(D)I and II16.In which reaction does the same element undergo both oxidation and reduction?(A)S8(s) + 8 O2(g) ? 8 SO2(g)(B)3 Br2(aq) + 6 OH- ? 5 Br- + BrO3- + 3 H2O (C)Ca2+ + SO42- ? CaSO4(s) (D)PtCI4(s) + 2 CI- ? PtCI62- 17.Which reaction is an oxidation-reduction reaction?(A)HC2H3O2(aq) + NH3(aq) ? C2H3O2- + NH4+(B)Ba2+ + SO42- ? BaSO4(s)(C)Zn(OH)2(s) + 2 OH- ? [Zn(OH)4]2-(D)2 K(s) + Br2(l) ? 2 KBr(s)18.10 HI + 2 KMnO4 + 3 H2SO4 ? 5 I2 + 2 MnSO4 + K2SO4 + 8 H2OHow many moles of HI are used to produce 2.5 mol of I2?(A)5.0 (B)8.0(C)10.(D)1219. 2 H2O + 4 MnO4- + 3 CIO2- ? 4 MnO2 + 3 CIO4- + 4 OH-How many moles of ClO2- react with 0.20 L of 0.20 M MnO4-?(A)0.030 (B)0.053 (C)0.075(D)0.1320.5 Fe2+ + MnO4- + 8 H+ ? 5 Fe3+ + Mn2+ + 4 H2O25.0 mL of an acidified Fe2+ solution requires 14.0 mL of 0.10-M MnO4- solution to reach the equivalence point. The concentration of Fe2+ in the original solution is(A) 0.10 M(B) 0.56 M(C) 0.28 M(D) 0.14 M21.Use the reduction potentials to determine which one of the reactions below is spontaneous.Cd2+ + 2 e- ? Cd-0.5 VCu+ + 1 e- ? Cu0.5 VMn2+ + 2 e- ? Mn-1.2 VFe3+ + 1 e- ? Fe2+0.7 V(A)Cd2+ + 2 Cu ? Cd + 2 Cu(B)Mn2+ + 2 Cu ? Mn + 2 Cu+(C)Cd2+ + Mn ? Cd + Mn2+(D)Cu+ + Fe3+ ? Cu + Fe2+22.According to the information below, what is the standard reduction potential for the half-reaction: M3+ + 3 e- ? M?M + 3 Ag+ ? 3 Ag + M3+ Eo = + 2.5 VAg+ + e- ? Ag Eo = + 0.8 V(A)-1.7 V(B)-0.1 V(C)0.1 V(D)1.7 V23.Magnesium reacts with dilute hydrochloric acid to produce hydrogen gas. Silver does not react in dilute hydrochloric acid. Based on this information, which of the following reactions will occur spontaneously?(A)H2(g) + Mg2+ ? 2 H+ + Mg(s)(B)2 Ag(s) + Mg2+ ? 2 Ag+ + Mg(s)(C)2 Ag+ + Mg(s) ? 2 Ag(s) + Mg2+(D)2 Ag + 2 H+ ? H2(g) + 2 Ag+24. Zn + Cu2+ ? Zn2+ + Cu Which could account for the observed voltage of 1.00 V instead of the standard cell potential, Eo, of 1.10 V?(A)The copper electrode was larger than the zinc electrode. (B)The Zn2+ electrolyte was Zn(NO3)2, while the Cu2+ electrolyte was CuSO4. (C)The concentration of the Zn2+ solution was greater than the Cu2+ solution. (D)The solutions in the half-cells had different volumes. Questions 25-26 refer to an electrolytic cell that involves the following half-reaction. AIF63- + 3 e- ? Al + 6 F-25. Which of the following occurs in the reaction? (A)AIF63- is reduced at the cathode.(B)Al is oxidized at the anode. (C)Aluminum is converted from the -3 oxidation state to the 0 oxidation state. (D)F- acts as a reducing agent. 26. A steady current of 10 A is passed through an aluminum-production cell for 15 minutes. Which of the following is the correct expression for calculating the number of grams of aluminum produced? (1 faraday = 96,500 coulombs) (A)(10)(15)(96,500)/(27)(60) (B)(10)(15)(27)/(60)(96,500) (C)(10)(15)(60)(27)/(96,500)(3)(D)(96,500)(27)/(10)(15)(60)(3)27. Which of the following expressions is correct for the maximum mass of copper, in grams, that could be plated out by electrolyzing aqueous CuCl2 for 16 hours at a constant current of 3.0 A? (1 faraday = 96,500 coulombs) (A)(16)(3,600)(3.0)(63.55)(2)/(96,500) (B)(16)(3,600)(3.0)(63.55)/(96,500)(2) (C)(16)(3,600)(3.0)(63.55)/(96,500) (D)(16)(60)(3.0)(96,500)(2)/(63.55) 28.If 0.060 faraday is passed through an electrolytic cell containing a solution of In3+ ions, the maximum number of moles of In that could be deposited at the cathode is (A) 0.010(B) 0.020 (C) 0.030(D) 0.060Questions 29-33 The spontaneous reaction that occurs when the cell below operates is 2 Ag+ + Cd ? 2 Ag + Cd2+Which occurs for each of the following circumstances?(A)Voltage increases.(B)Voltage decreases but remains above zero.(C)Voltage becomes zero and remains at zero(D)No change in voltage occurs29.A 50-mL sample of a 2-M Cd(NO3)2 solution is added to the left beaker.30.The silver electrode is made larger.31.The salt bridge is replaced by a platinum wire.32.Current is allowed to flow for 5 minutes.33.The silver electrode is replaced by a copper electrode.34. A power supply has lost the markings that indicate the positive and negative. A chemist suggests that the terminals be connected to a pair of platinum electrodes that dip into 0.1 M KI solution. Which correctly identifies the polarities of the terminals? (A)A gas will be evolved only at the positive electrode. (B)A gas will be evolved only at the negative electrode. (C)An amber color will appear near the negative electrode. (D)A metal will be deposited on the positive electrode. 35. In the electroplating of nickel, 0.200 faraday of electrical charge is passed through a solution of NiSO4. What mass of nickel is deposited? (A)2.94 g(B)5.87 g(C)11.7 g(D)58.7 gPractice Free Response1.A power supply is connected to two platinum electrodes immersed in a beaker containing 1.0 M CuSO4(aq) at 25oC. As the cell operates, copper metal is deposited on the left electrode and O2(g) is produced at the right electrode. The reduction half-reactions that occur are: O2(g) + 4 H+(aq) + 4 e- ? 2 H2O(l) Eo = +1.23 V Cu2+(aq) + 2 e- ? Cu(s) Eo = +0.34 Va.Is the direction of electron flow in the wire from left to right or from right to left? b.Write a balanced net ionic equation for the electrolysis reaction that occurs.A current of 1.50 A passes through the cell for 40.0 minutes.c.Calculate the mass of the Cu(s) that is deposited. d.Calculate the dry volume, in liters, measured at 25oC and 1.16 atm, of the O2(g) that is produced.2. A voltaic cell is constructed with a strip of Sn in a solution of Sn(NO3)2 in one container and a strip of an unknown metal, X, in a solution of X(NO3)3 in another container. The two containers are connected by a salt bridge and the two metal strips are connected with a metal wire. The mass of the Sn electrode increases. The half-reactions are: Sn2+(aq) + 2 e- ? Sn(s)Eo = -0.14 VX3+(aq) + 3 e- ? X(s)Eo = ?a.Which electrode is the cathode? Justify your answer. b.What directions do electrons flow in terms of the Sn and unknown metal strips. c.If the cell potential, Eocell, is + 0.60 V, what is the standard reduction potential for X3+(aq) + 3 e- ? X(s)?d.Identify metal X from the chart of standard potentials.e.Write a balanced net-ionic equation for the overall chemical reaction occurring in the cell. f.If the [Sn2+] = 0.50 M and [X3+] = 0.10 M. What is the cell potential, Ecell?3.An electrolytic cell contains a solution of Cr(NO3)3. Assume that chromium metal plates out at one electrode and oxygen gas is evolved at the other electrode.a.Write the anode half-reaction, the cathode half-reaction, and the overall reaction for the cell.b.How long will it take to deposit 15.0 g of chromium metal, using a current of 4.50 A?c.A current of 4.50 A is passed through the cell for 30.0 min. If we start out with 250 mL of 1.00 M Cr(NO3)3, what is the concentration of Cr3+ after electrolysis?A voltaic cell consists of two half-cells, one of which contains a Pt electrode surrounded by Cr3+ and Cr2O72- ions. The other half-cell contains a Pt electrode surrounded by Mn2+ ions and MnO2(s). Assume the cell reactions, which produce a positive voltage, involves both Cr3+ and Mn2+ ions.Cr2O72- + 14 H+ + 6 e- ? 2 Cr3+ + 7 H2OEored = 1.33 VMnO2(s) + 4 H+ + 2 e- ? Mn2+ + 2 H2OEored = 1.229 Vd.Write the anode half-reaction, the cathode half-reaction, and the overall reaction for the cell.e.Calculate Eotot for the cell.f.Calculate the voltage of the cell when all ionic species except H+ have a concentration of 0.300 M and the solution has [H+] = 3.16 x 10-4 M.4. An electrochemical cell is constructed with an open switch, as shown in the diagram above. A strip of Sn and a strip of an unknown metal, X, are used as electrodes. When the switch is closed, the mass of the Sn electrode increases. The half-reactions are shown below. Sn2+ + 2 e- ? Sn(s)Eo = -0.14 VX3+ + 3 e- ? X(s) Eo = ?a.In the diagram above, label the electrode that is the cathode. Justify your answer. b.In the diagram above, draw an arrow indicating the direction of the electron flow in the external circuit when the switch is closed. c.If the standard cell potential, Eocell, is + 0.60 V, what is the standard reduction potential, in volts, for the X3+/X electrode? d.Identify metal X. e.Write a balanced net-ionic equation for the overall chemical reaction occurring in the cell. f.In the cell, the concentration of Sn2+ is changed from 1.0 M to 0.50 M, and the concentration of X3+ is changed from 1.0 M to 0.10 M. (1)Substitute all the appropriate values for determining the cell potential, Ecell, into the Nernst equation. (Do not do any calculations.) (2)On the basis of your response in part (f) (1), will the cell potential, Ecell, be greater than, less than, or equal to the original Eocell? Justify your answer. ................
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