Determining the oxidation half reactions for an equation

Balance the following equation and determine the sum of the coefficients of the products

1) Balance the following equation and determine the sum of the coefficients of the products.

___NO2- + ___MnO4- + ___ H2O à ___ NO3- + ___ MnO2 + ___ OH-

A. 3
B. 4
C. 5
D. 6
E. 7

2) Balance the following redox equation and determine the sum of the coefficients of the reactants and products.

___ Br2 + ___ SO2 + ___ H2O à ___ H+ + ___ Br- + ___ SO2-

A. 9
B. 10
C. 11
D. 12
E. 13

3) Which type of reaction is occurring when a metal undergoes corrosion?

A. oxidation-reduction
B. neutralization
C. polymerization
D. saponification
E. decomposition

4) Given the reaction for the nickel-cadmium battery 2NiOH + Cd +2H2O à 2Ni(OH)2 + Cd(OH)2

What species is oxidized during the discharge of the battery?

A. Ni3+
B. Ni2+
C. Cd
D. Cd2+

E. not enough information provided

5) Given the redox reaction 2I-(aq) + Br2(l) à 2Br-(aq) + I2(s)

What occurs during this reaction?
A. The I- ion is oxidized, and its oxidation number increases.
B. The I- ion is oxidized, and its oxidation number decreases.
C. The I- ion is reduced, and its oxidation number increases.
D. The I- ion is reduced, and its oxidation number decreases.
E. none of the above

6) Which half-reaction correctly represents reduction?

A. Cr3+ + 3e- à Cr(s)
B. Cr3++ à Cr(s) + 3e-
C. Cr(s) à Cr3+ + 3e-
D. Cr(s) + 3e- à Cr3+
E. none of the above

7) What is the oxidation number of carbon in NaHCO3?

A. +6
B. +2
C. -4
D. +4
E. not enough information given

8) When a substance is oxidized, it

A. loses protons
B. gains protons
C. acts as an oxidizing agent
D. acts as a reducing agent
E. none of the above

9) A battery consists of which type of cells?

A. electrolytic
B. electrochemical
C. electroplating
D. electromagnetic
E. none of the above

10) Given the lead-acid battery reaction Pb + PbO2 + H2SO4 Discharge à Charge ß 2 PbSO4 + 2 H2O

Which species is oxidized during battery discharge?

A. Pb
B. PbO2
C. SO42-
D. 2 H2O
E. not enough information given

11) Chromium is reduced from CrO42- (aq) to Cr(OH)4- (aq) in an electrolytic cell. What mass of Cr(OH)4- (aq) is formed by passage of 4.50 A for a period of 8000 seconds?

A. 10.4
B. 14.4
C. 21.2
D. 34.4
E. 44.8

12) Given the reaction for the nickel-cadmium battery 2 NiOH + Cd +2 H2O à 2 Ni(OH)2 + Cd(OH)2

What species is oxidized during the discharge of the battery?

A. Ni3+
B. Ni2+
C. Cd
D. Cd2+
E. not enough information given

13) A NiSO4 solution is electrolyzed using a current of 1.25 A. How many grams of Ni plate out in 25.0 min?

A. 0.570
B. 0.690
C. 0.820
D. 0.980
E. 1.14

14) How many minutes are required to plate out 5.00 g of tellurium from a solution containing TeO32- using a current of 1.60 A?

A. 158
B. 220
C. 276
D. 316
E. 356

15) How many minutes would be required to reduce 21.0 g of Na2[CdCl4] to metallic cadmium with a current of 7.5 A?

A. 15
B. 20
C. 30
D. 40
E. 60

16) A 1.0 M solution of Fe2+ is added to excess solid zinc and the system is allowed to reach equilibrium. What is the concentration of Fe2+?

2 Fe2+ (aq) + Zn (s) ó 2 Fe (s) + Zn2+ (aq)

Eº = 0.323

A. 6.1 x 10-12
B. 5.5 x 10-8
C. 4.5 x 10-7
D. 3.5 x 10-6
E. 2.5 x 10-6

17) Which is the best description of one faraday?

A. 8.31 joules
B. 96,500 amperes
C. one coulomb / volt
D. one joule / coulomb
E. 6.02 x 1023 electrons

18) Consider the reaction H2O + Br2 à HOBr + HBr

Which is the best description of the behavior of bromine in the reaction above?

A. oxidized only
B. proton donor
C. proton acceptor
D. both oxidized and reduced
E. neither oxidized nor reduced

19) A voltaic cell that uses the following reaction has a measured emf of 1.19 V under standard conditions. The standard electrode potential for Cr3+ is -0.408 V. What is Eº for the indicated reduction of Tl3+ ?

Tl3+ (aq) + 2 Cr2+ (aq) ó Tl+ (aq) + 2 Cr3+ (aq)

Cr3+ + e- à Cr2+

Tl3+ (aq) + 2 e- à Tl+ (aq)

A. +0.88
B. +1.10
C. +0.78
D. +1.12
E. +1.60

20) The Eº = 1.24 V for the following reaction. The standard electrode potential for O2 as written is -0.56 V. What is the standard electrode potential for the reduction of H2BO3- ?

H2BO3- (aq) + 5 H2O (l) + 8 O2- (aq) ó BH4- (aq) + 8 OH- (aq) + 8 O2 (g)

O2 (g) + e- à O2- (aq)

5 H2O (l) + H2BO3- (aq) + 8 e- à BH4- (aq) + 8 OH- (aq)

A. +0.68
B. +0.90
C. -0.68
D. +1.80
E. -1.80

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