Chapter 20 Practice Questions

1 Chapter 20 multiple choice . Choose the one alternative that best completes the statement or answers the )The gain of electrons by an element is called )oxidationB)reductionC)sublimationD)frac tionationE)disproportionation1)2)_____ is reduced in the following reaction:Cr2O72 + 6S2O32 + 14H+ 2Cr3+ + 3S4O62 + 7H2OA)S2O32 B)Cr3+C)H+D)Cr2O72 E)S4O62 2)3)_____ is the oxidizing agent in the reaction below. Cr2O72 + 6S2O32 + 14H+ 2Cr3+ + 3S4O62 + 7H2OA)H+B)Cr3+C)S2O32 D)S4O62 E)Cr2O72 3)4)Which substance is serving as the reducing agent in the following reaction?

2 14H+ + Cr2O72 + 3Ni 3Ni2+ + 2Cr3+ + 7H2OA)H2OB)NiC)Cr2O72 D)Ni2+E)H+4)5)Which substance is the reducing agent in the reaction below?Pb + PbO2 + 2H2SO4 2 PbSO4 + 2H2OA)PbSO4B)PbO2C)H2SO4D)PbE)H2O5)6)Wha t is the oxidation number of chromium in Cr2O2 7 ion ?A)+12B)+14C)+6D)+3E)+76)7)What is the oxidation number of potassium in KMnO4?A)+3B)0C)+1D) 1E)+27)18)What is the oxidation number of manganese in the MnO1 4ion?A)+4B)+2C)+7D)+1E)+58)9)What is the oxidation number of manganese in MnO2?A)+2B)+7C)+1D)+4E)+39)10)_____ electrons appear in the following half reaction when it is 2S2O32 A)2B)4C)6D)3E)110)11)The balanced half reaction in which chlorine gas is reduced to the aqueous chloride ion is a_____ )two electronB)six electronC)four electronD)one electronE)three electron11)12)The balanced half reaction in which dichromate ion is reduced to chromium metal is a )two electronB)six electronC)twelve electronD)four electronE)three electron12)13)

3 The balanced half reaction in which dichromate ion is reduced to chromium(III) ion is a_____ )three electronB)six electronC)twelve electronD)two electronE)four electron13)214)The balanced half reaction in which sulfate ion is reduced to sulfite ion is a _____ )six electronB)one electronC)four electronD)two electronE)three electron14)15)The electrode at which oxidation occurs is called the _____ .A)cathodeB)oxidizing agentC)reducing agentD)voltaic cellE)anode15)16)The half reaction occurring at the anode in the balanced reaction shown below is (aq) + 24H+ (aq) + 5Fe (s) 3Mn2+ (aq) + 5Fe3+ (aq) + 12H2O (l)A)2 MnO4 (aq) + 12H+ (aq) + 6e 2Mn2+ (aq) + 3H2O (l)B)MnO4 (aq) + 8H+ (aq) + 5e Mn2+ (aq) + 4H2O (l)C)Fe (s) Fe3+ (aq) + 3e D)Fe2+ (aq) Fe3+ (aq) + e E)Fe (s) Fe2+ (aq) + 2e 16)17)In a voltaic cell, electrons flow from the _____ to the )cathode, anodeB)

4 Salt bride, anodeC)anode, cathodeD)anode, salt bridgeE)salt bridge, cathode17)18)The reduction half reaction occurring in the standard hydrogen electrode is )2H+ (aq) + 2OH H2O (l)B)O2 (g) + 4H+ (aq) + 4e 2H2O (l)C) 2H+ (aq, 1M) + Cl2 (aq) 2 HCl (aq)D)H2 (g, 1 atm) 2H+ (aq, 1M) + 2e E) 2H+ (aq, 1M) + 2e H2 (g, 1 atm)18)319)1V = )1 J/sB)96485 CC)1 J/CD)1 amp sE)1 C/J19)20)The more _____ the value of E red, the greater the driving force for )exothermicB)extensiveC)endothermicD)neg ativeE)positive20)Table reaction E (V)Cr3+ (aq) + 3e Cr (s) + (aq) + 2e Fe (s) + (aq) + e Fe2+ (s)+ + (aq) + 2e Sn2+ (aq)+ )The standard cell potential (E cell) for the voltaic cell based on the reaction below is _____ + (aq) + 2Fe3+ (aq) 2Fe2+ (aq) + Sn4+ (aq)A)+ )+ )+ ) )+ )22)The standard cell potential (E cell) for the voltaic cell based on the reaction below is _____ (s) + 3Fe3+ (aq) 3Fe2+ (aq) + Cr3+ (aq)A)+ ) )+ )+ )+ )23)

5 The standard cell potential (E cell) for the voltaic cell based on the reaction below is _____ (s) + 3Fe2+ (aq) 3Fe (s) + 2Cr3+ (aq)A) )+ )+ )+ )+ )24)The standard cell potential (E cell) for the voltaic cell based on the reaction below is _____ + (aq) + 2Cr (s) 2Cr3+ (aq) + 3Sn2+ (aq)A)+ ) )+ ) )+ )425)The relationship between the change in Gibbs free energy and the emf of an electrochemical cell isgiven by ) G = nFERTB) G = nFEC) G = EnFD) G = nFEE) G = nRTF25)26)The standard cell potential (E cell) of the reaction below is + V.

6 The value of G for thereaction is _____ (s) + 2H+ (aq) Pb2+ (aq) + H2 (g)A) 24B)+24C) 12D)+12E) 5026)27)The standard cell potential (E cell) for the reaction below is + V. The cell potential for thisreaction is _____ V when [ Zn2+] = M and [Pb2+] = 10 4 + (aq) + Zn (s) Zn2+ (aq) + Pb (s)A) ) ) ) ) )28)The standard cell potential (E cell) for the reaction below is + V. The cell potential for thisreaction is _____ V when the concentration of [Cu2+] = 10 5 M and [Zn2+] = (s) + Cu2+ (aq) Cu (s) + Zn2+ (aq)A) ) ) ) ) )29)The lead containing reactant(s) consumed during recharging of a lead acid battery )PbO2 (s) onlyB)Pb (s) onlyC)PbSO4 (s) onlyD)both PbO2 (s) and PbSO4 (s)E)both Pb (s) and PbO2 (s)29)530)Galvanized iron is iron coated with ) ) ) ) )iron )31)Corrosion of iron is retarded by )the presence of saltsB)low pH conditionsC)high pH conditionsD)

7 Both the presence of salts and high pH conditionsE)both the presence of salts and low pH conditions31)32)How many minutes will it take to plate out g of chromium metal from a solution of Cr3+ usinga current of amps in an electrolyte cell _____ ?A) )115C)346D) ) )33)What current (in A) is required to plate out g of nickel from a solution of Ni2+ in hour_____ ?A) ) ) ) ) 10333)34)How many grams of Ca metal are produced by the electrolysis of molten CaBr2 using a current amp for hours _____ ?A) )448C) )112E)22434)35)How many grams of CuS are obtained by passing a current of 12 A through a solution of CuSO4for 15 minutes _____ ?

8 A) ) )14D) ) )36)How many seconds are required to produce g of silver metal by the electrolysis of a AgNO3solution using a current of 30 amps _____ ?A) 10 5B)60C) 103D)30E) 10436)37)How many grams of copper will be plated out by a current of A applied for 25 minutes to M solution of copper(II) sulfate _____ ?A) ) ) ) ) 10 237)6 Answer KeyTestname: Chapter 20 Practice QUESTIONS1)B2)D3)C4)B5)D6)C7)C8)C9)D10)A 11)A12)C13)B14)D15)E16)C17)C18)E19)C20)E 21)A22)C23)E24)C25)D26)A27)E28)A29)C30)A 31)C32)E33)C34)E35)A36)D37)D7