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1) Which most readily gains electrons?

 Cu Cu+2 Fe+2 Zn+2 Au+3 most readily gains electrons

2) Which most readily loses electrons?

 Hg(l) Cu+2 Sn+4 Ba most readily loses electrons Al

Calculate the cell potentials or voltages (E0). Indicate spontaneity.

3. Cl2 + 2Br- -----> 2Cl- + Br2 E0= + 0.27 v spontaneous

4. 2MnO4- + 5Pb + 16H+ -----> 2Mn+2 + 8H2O + 5Pb+2 E0= + 1.64 v spontaneous

5. Will AgNO3 react with Zn? Write a balanced redox reaction and calculate Eo

2Ag+ + Zn ------> 2Ag + Zn+2 E0= + 1.56 v spontaneous Yes!

6. What would happen if you used an iron spoon to stir a soulution of Al2(SO4)3(aq) ? Write a balanced redox reaction and calculate Eo.

3Fe + 2Al+3 ------> 3Fe+2 + 2Al E0= - 1.21 v nonspontaneous No reaction!

7) What are the differences between an electrochemical cell and an electrolytic cell?

 electrochemical cell electrolytic cell Produces electricity Consumes electricity Spontaneous Nonspontaneous Salt bridge Two beakers No salt bridge One beaker Metal Electrodes Inert C or Pt Electrodes

8) What are the similarities between an electrochemical cell and an electrolytic cell?

 electrochemical cell or electrolytic cell The Anode is the site of oxidation and the cathode is the site of reduction. Anions migrate to the anion and cations migrate to the cathode. Both have redox reactions. Electrons flow through a wire from the anode to the cathode

9) State how you would determine each of the following in an electrochemical or electrolytic cell.

 Electrochemical Cell Electrolytic Cell The site of reduction Highest on Reduction Chart The Negative Electrode The site of oxidation Lowest on Reduction Chart The Positive Electrode The +ve electrode Site of Reduction Connected to the power supply +ve The -ve electrode Site of Oxidation Connected to the power supply -ve The anions migrate to the Anode Anode The cations migrate to the Cathode Cathode The electrode that gains mass Cathode Neither inert electrodes The electrode that loses mass Anode Neither inert electrodes The electrons flow from Anode to Cathode Anode to Cathode

10.a) Draw an operating electrochemical cell using an Al half-cell and a Mg half-cell. Label the parts of the electrochemical cell including the anode or cathode, and all reagents and materials used. Write the reactions and determine the E0.

Cathode Reaction: 2(Al+3 + 3e- ------> Al ) E0= - 1.66

Anode Reaction: 3(Mg -------> Mg+2 + 2e- ) E0= +2.37

Redox Reaction: 2Al+3 + 3Mg -----> 3 Mg+2 + 2 Al E0= +0.71

11. (a) Write the half reaction that occurs at each electrode during the electrolysis of aqueous 1 M NaI.

Anode : 2I- --------> I2 + 2e- E0= -0.54 v

`Cathode :  2H2O   +   2e-   ------>   H2    +   2OH-     E0= -0.41v`

(b) What is the minimum required voltage for this process? E0= +0.95 v

12. (a) Write the half reaction that occurs at each electrode during the electrolysis of molton NaI.

Anode : 2I- --------> I2 + 2e- E0= -0.54 v

Cathode : Na+ + 1e- ------> Na E0= -2.71v

(b) What is the minimum required voltage for this process? E0= +3.25v

13. Aluminum is produced industrially from aluminum oxide, Al2O3. Demonstrate your understanding of this process by

(i) describing how the process is carried out: C electrodes are used in the electrolysis of molten Al2O3.

(ii) writing equations of the reactions involved in the process, and

Anode : 2O-2 --------> O2 + 4e- Cathode : Al+3 + 3e- ------> Al

(iii) describing how the problem of the high melting point of Al2O3 is overcome.

Mixing Al2O3 with cryolyte lowers the melting point from 2000º C to 900ºC, which is suitable for electrolysis.

14. Consider the following redox data:

3V + 2Ga3+ ----> 3V2+ + 2Ga E=+0.64V

3V2+ + 2Al ----> 3V + 2 Al3+ E=+0.46V

Based on these observations, a student concludes that Ga+3 and Al will react spontaneously. List the oxidizing agents in order of decreasing strength. Write reduction reactions for each. Determine the strongest reducing agent. Determine if Ga+3 and Al will react spontaneously.

 strongest oxidizing agent Ga3+ + 3e- ----> Ga V2+ + 2e- ----> 3V Al3+ + 3e- ----> Al strongest reducing agent

Ga+3 and Al will react spontaneously as Ga+3 is a stronger oxidizing agent than Al+3.

15. Balance the equation for the following half reaction occuring in acid solution:

7 H2O + 2V ----> HV2O7-3 + 13H+ + 10e-

16. Balance the following redox reaction occuring in basic solution:

4 H2O + 2 MnO4- + 3 C2O4-2 -----> 2 MnO2 + 8 OH- + 6 CO2

17. 250ml .200M MnO4- reacts with excess SO3-2. How many grams of MnO2 are produced?

2MnO4- + 3SO3-2 + H2O -----> 2MnO2 + 3SO4-2 + 2OH- 4.35g MnO2

18. Determine the oxidation number for each bold atom.

 MnO2 IO3- Cr2O7-2 C2O4-2 Al(NO3)3 NH4Cl NaH +4 +5 +6 +3 +3 -3 -1 HOOH NO3- H3PO4 Na2C2O4 I2 N2O3 Pt(H2O)4+2 -1 +5 +5 +3 0 +3 +2

19. 250ml of .500M MnO4- are required to titrate a 100ml sample of SO3-2. Calculate the [SO3-2]

2MnO4- + 3SO3-2 + H2O -----> 2MnO2 + 3SO4-2 + 2OH- [SO3-2] = 1.88M

20. How is the breathalyzer reaction used to determine BAC? Write the reaction and describe how it works. BAC is blood alcohol concentration which is related to the concentration of alcohol in the breath. The alcohol in a breath sample reacts with Cr2O7-2 reducing the orange color of the solution.

8 H+ + Cr2O7-2 (orange) + 3C2H5OH ------> 2Cr+3 (green) + 3C2H4O + 7H2O

21. 2H+ + Mg-----> Mg+2 +H2

Determine the Oxidizing agent H+ and the Reducing agent Mg

22. Choose a suitable redox reactant to oxidize Cl- to ClO4- in a redox titration. MnO4- in acid

23. Describe as an electrochemical or electrolytic cell:

 a) Fuel cell electrochemical b) Charging a car battery electrolytic c) Discharging a car battery electrochemical d) Ni plating electrolytic e) Industrial Al production electrolytic f) Cl2 production electrolytic g) Electrowinning electrolytic

24) Which of the reactants is gaining electrons? Which of the reactants is the oxidizing agent?

Br2 (oxidizing agent and is gaining electrons) + SO2 +Na2SO4 +H2O --------> 2H2SO4 + 2NaBr

25) A student studied the following reactions and she recorded:

Pd+2 + Cu -------> Pd + Cu+2 spontaneous

Pd+2 + Au -------> no reaction

Pd+2 + Hg -------> no reaction

Au+3 + Hg -------> Au + Hg+2 spontaneous

List the oxidizing agents from strongest to weakest. List the reducing agents from strongest to weakest. Predict if the reaction will occur.

 Strongest Oxidizing agent Au+3 + 3e- -------> Au Hg+2 + 2e- -------> Hg Pd+2 + 2e- -------> Pd Cu+2 + 2e- -------> Cu Weakest Reducing Agent

Au+3 + Cu ------------> Yes Spontaneous Reaction

26) Match each type of electrolytic cell with the example cell.

 Electrowinning Pure Al is reduced at the cathode from molten bauxite (Al2O3). Electroplating A silver anode oxidizes & Ag reduces on a Cu cathode Electrorefining Pure Pb is reduced at the cathode while impure Pb oxidizes at the anode

27. List the anode, cathode, anode reaction , cathode reaction, and electrolyte for each commercial electrochemical cell.

 Cell anode anode reaction cathode cathode reaction electrolyte Leclanche or Common Dry Cell Zn Zn-->Zn+2 + 2e- C/MnO2 Mn+4 +1e- -----> Mn+3 NH4Cl Alkaline Cell Zn Zn-->Zn+2 + 2e- C/MnO2 Mn+4 +1e- -----> Mn+3 KOH Lead Storage or Car Battery Pb Pb ---> Pb+2+ 2e- PbO2 PbO2 + SO4-2 + 4OH-1 + 2e- -----> PbSO4 + 2H2O H2SO4 Fuel Cell C H2 + 2OH- ---> 2H2O + 2e- C O2 + 2H2O +4e-----> 4OH- KOH

28. Which of the above cells requires continuous input of O2 and H2 and is produced by Ballard Industries. Fuel Cell

29. List the anode, cathode, anode reaction , cathode reaction, and electrolyte for each commercial electrolytic cell.

 Cell anode anode reaction cathode cathode reaction electrolyte Electrolysis of Molten Al2O3 C O-2 ---> O2 + 2e- C Al+3 + 3e- ---> Al Molten Al2O3 Electrolysis of Aqueous NaCl C 2Cl- ----> Cl2 + 2e- C 2H2O + 2e-----> H2 + 2OH- Aqueous NaCl Silver-plating a Cu spoon Ag Ag ---> Ag+ + 1e- Cu Ag+ + 1e- ---> Ag AgNO3(aq) Electrorefining pure Pb from impure Pb Impure Pb Pb ---> Pb+2 + 2e- Pure Pb Pb+2 + 2e- ---> Pb PbSiF6

30. Describe each term:

 salt bridge U-tube filled with salt solution connecting two half cells in a electrochemical cell. Allows ions to migrate. electrolyte A solution that contains ions and conducts electricity. anode Metal electrode that is the site of oxidation. cathode Metal electrode that is the site of reduction. spontaneous Occurs naturally and has a positive Eo. electronegativity The ability to attract electrons. cation Positive ion. anion Negative ion. electrochemical cell Two metals in electrolytes joined by a salt bridge using spontaneous redox reaction to produce an electrical current. electrolytic cell A power supply connected to inert electrodes in an electrolyte which forces nonspontaneous redox reactions to occur. oxidation number The real or apparent charge of an atom if all bonds are assumed to be ionic. electrolysis What occurs in an electrolytic cell. oxidation Loss of electrons. reduction Gain of electrons. oxidizing agent Causes oxidation by undergoing reducing. reducing agent Causes reduction by undergoing oxidation. electrode Strip of C or Metal used in a cell. corrosion The oxidation of a metal often Fe ---> Fe+2 + 2e- electrowinning The reduction of a metal from its ore by electrolysis. electrorefining The purification of a metal by electrolysis. overpotential effect The higher than normal voltage for the oxidation and reduction of water. fuel cell An electrochemical cell that converts H2 and O2 into H2O and electricity.

31. Define corrosion of a metal, and illustrate your definition with reference to an example, using appropriate equations. Give TWO methods by which corrosion can be prevented and describe how each method works. The two methods must involve different chemical principles.

The corrosion of iron Cathode: Fe ----> Fe+2 + 2e-

Anode: O2 + 2H2O + 4e- ------> 4OH-

1) Painting prevents the reactants: O2 + 2H2O from colliding with the surface of the metal.

2) Galvinizing allows Zn to corrode (anode) instead of Fe (cathode) due to the action of the chemical cell they produce.

32. Explain why you would choose Zn or Cu to cathodically protect iron? Zn because it oxidizes more readily than Fe forcing Fe to be the cathode or site of reduction.

33. A+2 does not react with B, while C+2 reacts with B. Rank the oxidizing agents in decreasing order of strength. Rank the reducing agents in decreasing order of strength. Will A+2 react with C?

C+2 + 2e- --------> C Oxidizing agents: C+2 B+2 A+2

B+2 + 2e- --------> B Reducing Agents: A B C

A+2 + 2e- --------> A

A+2 will not react with C.

34. Write half reactions for each using the reduction table and list the half cell potential.

 Half Reaction Eo oxidation of water H2O --------> 1/2 O2 + 2H+ + 2e- -0.82v oxidation of water in acid 2 H2O --------> 1/2O2 + 2H+ + 2e- -1.23v reduction of water 2 H2O + 2e- ------------> H2 + 2OH- -0.41v reduction of water in alkaline 2 H2O + 2e- ------------> H2 + 2OH- -0.83v oxidation of H2 in water H2 + 2OH- ------------> 2 H2O + 2e- +0.41 oxidation of H2 in acid H2 ------------> 2H+ + 2e- 0.00v oxidation of H2 in base H2 + 2OH- ------------> 2 H2O + 2e- +0.83 reduction of Cr2O7-2 in acid Cr2O7-2 + 14 H+ + 6 e- -------> 2Cr3+ + 7 H2O +1.23v reduction of HBr 2H+ + 2e- ------------> H2 0.00v

35.Completely analyze the following electrochemical cell. The anode reaction is: Zn -----------> Zn+2 + 2e- The cathode reaction is: Cu+2 + 2e- -------> Cu The electrons flow from ___ to ___ anode to cathode The ions that migrate to the Zn electrode are: NO3- The ions that migrate to the Cu electrode are: Zn+2 Cu+2 K+ The intial voltage of this cell is: 1.10v The voltage of this cell once equilibrium is reached is: 0.00v Describe the change in [Cu+2] in the Cu half cell decreases Describe the change in [NO3-1] in the Zn half cell increase

36. Completely analyze the following electrochemical cell. The anode reaction is: H2 ------------> 2H+ + 2e- The cathode reaction is: Cu+2 + 2e- -------> Cu The electrons flow from ___ to ___ anode to cathode The ions that migrate to the Pt electrode are: NO3- Cl- The ions that migrate to the Cu electrode are: Cu+2 K+ H+ The intial voltage of this cell is: 0.34v The voltage of this cell once equilibrium is reached is: 0.00v Describe the change in [Cu+2] in the Cu half cell decreases Describe the change in [NO3-1] in the H+/H2 half cell increases

38.       Completely analyze the following electrolytic cell. Note that the electrodes are not inert and because of that, the anode might oxidize. Anode Reaction Cu   ®   Cu2+  +  2e-                                  E0  = -0.34 v Cathode Reaction 2H2O +  2e-  ®  H2  +  2OH-                       E0  = -0.41 v Chemicals produced at the anode Cu2+ Chemicals produced at the cathode H2      OH- The electrons flow from Anode (right) to cathode (left) The MTV +0.75 v Which electrode is the anode ? right

38. Completely analyze the following electrolytic cell. Anode Reaction 2O-2 ---------> O2 +4e- Cathode Reaction Al+3 + 3e- ---------> Al Chemicals produced at the anode O2 Chemicals produced at the cathode Al The electrons flow from __to __ anode to cathode The chemical used to lower the mp is: cryolite Which electrode is the anode ? the one on the right

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