Chemistry: Molecular Nature of Matter and Change, 6th Edition (Silberberg)

Chapter 21: Electrochemistry: Chemical Change and Electrical Work

Self-Assessment Quiz 1

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1			Which of the following statements is incorrect?
			A)	In an electrolytic cell, reduction occurs at the anode.
			B)	Aluminum metal would form at the cathode during the electrolysis of molten AlBr3.
			C)	The cathode is labeled "+" in a voltaic cell.
			D)	Oxidation occurs at the anode in a voltaic cell.
			E)	Electrons flow from the anode to the cathode in all electrochemical cells.
2			Consider the following notation for an electrochemical cell Zn|Zn2+ (1M)||Fe2+ (1M), Fe3+ (1M)|Pt What is the balanced equation for the cell reaction?
			A)	Zn(s) + 2Fe3+(aq) → 2Fe2+(aq) + Zn2+(aq)
			B)	Zn2+(aq) + 2Fe2+(aq) → Zn(s) + 2Fe3+(aq)
			C)	Zn(s) + 2Fe2+(aq) → 2Fe3+(aq) + Zn2+(aq)
			D)	Zn(s) + Fe3+(aq) → Fe2+(aq) + Zn2+(aq)
			E)	Zn(s) + Fe2+(aq) → Fe(s) + Zn2+(aq)
3			A voltaic cell is constructed from the following half-cells, linked by a KCl salt bridge: (a) an Fe electrode in 1.0 M FeCl2 solution (b) a Ni electrode in 1.0 M Ni(NO3)2 solution Use the table of standard electrode potentials in your textbook to decide which one of the following statements is correct.
			A)	The Ni electrode is the anode.
			B)	Electrons flow from the iron electrode to the nickel electrode.
			C)	The iron electrode is positively charged.
			D)	The iron electrode will gain mass when current flows.
			E)	The salt bridge conducts electrons through solution.
4			Consider the electrochemical cell: Zn(s) | Zn2+(aq) || Br-(aq) | Br2(l) | Pt Use data from the table of standard electrode potentials in your textbook to calculate the standard potential of this cell, E°cell.
			A)	0.31 V
			B)	1.83 V
			C)	-0.31 V
			D)	1.30 V
			E)	none of the above
5			When combined with a Cu2+/Cu electrode (E° = 0.34V), which of the following electrodes will produce the largest standard cell potential?
			A)	M+/M, E° = 1.00 V
			B)	M2+/M, E° = 0.90 V
			C)	X2/X-, E° = 0.95 V
			D)	M2+/M, E° = -0.30 V
			E)	M+/M, E° = -0.50 V
6			Consider the following half-reactions and select the strongest oxidizing agent present: Sr2+(aq) + 2e- → Sr(s) E° = -2.89 V Cr2+(aq) + 2e- → Cr(s) E° = -0.913 V Co2+(aq) + 2e- → Co(s) E° = -0.28 V
			A)	Cr2+(aq)
			B)	Sr2+(aq)
			C)	Co2+(aq)
			D)	Sr(s)
			E)	Co(s)
7			Given the following standard reduction potentials in acid solution: Al3+(aq) + 3e- → Al(s) E° = -1.66 V Sn4+(aq) + 2e- → Sn2+(aq) E° = +0.14 V I2(s) + 2e- → 2I-(aq) E° = +0.53 V Which of the following is the strongest reducing agent?
			A)	Al3+(aq)
			B)	Al(s)
			C)	I-(aq)
			D)	I2(s)
			E)	Sn4+(aq)
8			A redox reaction that involves the transfer of 3 electrons has a standard cell potential of +0.34 V. Calculate ΔG° for this reaction (F = 96500 C/mol).
			A)	-98 kJ
			B)	-32 kJ
			C)	+98 kJ
			D)	+32 kJ
			E)	-8.3 kJ
9			If the equilibrium constant Kc is greater than 1 for a given reaction, predict the signs of ΔG° and E° at the same temperature.
			A)	ΔG° > 0; E° > 0
			B)	ΔG° < 0; E° < 0
			C)	ΔG° > 0; E° < 0
			D)	ΔG° < 0; E° > 0
			E)	Cannot predict - it depends on the temperature.
10			A voltaic cell consists of Mn/Mn2+ and Cd/Cd2+ half-cells. At 25°C the cell potential is +0.768 V when the concentration of Mn2+ ions is 0.500 M. Use the Nernst equation to calculate the Cd2+ concentration. Standard electrode potentials are given below. (F = 96500 C/mol) Cd2+(aq) + 2e- → Cd(s) E° = -0.402 V Mn2+(aq) + 2e- → Mn(s) E° = -1.182 V
			A)	0.010 M
			B)	0.050 M
			C)	0.20 M
			D)	0.50 M
			E)	0.25 M
11			Which of the following statements about fuel cells is correct?
			A)	Fuel cells are electrolytic cells used to produce fuels such as H2.
			B)	Fuel cells are galvanic cells used to produce fuels such as H2.
			C)	Fuel cells are secondary cells.
			D)	Fuel cells have similar energy efficiency to electric power stations.
			E)	None of the above statements is correct.
12			Which of the following statements about the corrosion of iron is incorrect?
			A)	Moisture is necessary in order for iron to corrode.
			B)	Oxygen acts as an oxidizing agent in iron corrosion.
			C)	Corrosion occurs more rapidly at high pH.
			D)	Corrosion occurs more rapidly in the presence of conducting solutions.
			E)	Corrosion of iron slows down when the iron is in contact with zinc metal.
13			Which one of the following reactions must be carried out in an electrolytic cell, rather than a voltaic cell?
			A)	Zn + Cd2+ → Cd + Zn2+
			B)	Al + 3/2Br2 → Al3+ + 3Br-
			C)	2Al3+ + 3Fe → 2Al + 3Fe2+
			D)	H2 + I2 → 2H+ + 2I-
			E)	2H2 + O2 → 2H2O
14			In an electrolytic cell, how many grams of Cu could be plated out of a CuSO4 solution at a current of 5.00 A for 2.00 min? (F = 96500 C/mol)
			A)	318 g
			B)	0.395 g
			C)	0.329 x 10-3 g
			D)	0.198 g
			E)	5.31 g
15			How many minutes does it take to plate 0.800 g of silver metal onto a serving tray from an aqueous solution of AgNO3 at a current of 2.50 A? (F = 96500 C/mol)
			A)	< 2 minutes
			B)	2.38 minutes
			C)	4.77 minutes
			D)	9.54 minutes
			E)	23.8 minutes

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