Chapter 18 BANK

Chapter 21: Electrochemistry

Page 1

CHAPTER 21 ELECTROCHEMISTRY 21-1.

Consider an electrochemical cell formed from a Cu(s) electrode submerged in an aqueous Cu(NO3)2 solution and a Cd(s) electrode submerged in a Cd(NO3)2(aq) solution. The two electrodes are connected by a wire and the two solutions are connected by a salt bridge containing NaNO3(aq). The following reaction takes place: Cu 2+ (aq) + Cd(s) → Cu(s) + Cd2+ (aq) Which statement describes how the electrons or nitrate ions will flow?

21-2.

(a)

electrons will flow from Cu(s) to Cd(s)

(b)

nitrate ions will flow from Cu compartment to Cd compartment

(c)

nitrate ions will not flow between compartments

(d)

nitrate ions will flow from Cd compartment to Cd compartment

Consider an electrochemical cell formed from a Cu(s) electrode submerged in an aqueous Cu(NO3)2 solution and a Cd(s) electrode submerged in a Cd(NO3)2 solution. The two electrodes are connected by a wire and the two solutions are connected by a salt bridge containing NaNO3(aq). The following reaction takes place: Cu 2+ (aq) + Cd(s) → Cu(s) + Cd2+ (aq) Which statement describes how the electrons or nitrate ions will flow?

21-3.

(a)

electrons will flow from Cu(s) to Cd(s)

(b)

electrons will flow from Cd(s) to Cu(s)

(c)

electrons will not flow between electrodes

(d)

nitrate ions will flow from Cd compartment to Cd compartment

Consider an electrochemical cell where the following reaction takes place: 2 Au3+ (aq) + 3 Zn(s) → 2 Au(s) + 3 Zn2+ (aq) Which of the following is the correct cell notation for this cell? (a)

Au | Au 3+ || Zn 2+ | Zn

(b)

Au3+ | Au || Zn | Zn2+

(c)

Zn | Zn 2+ || Au 3+ | Au

(d)

Zn | Au 3+ || Au | Zn2+

NOTE: for spring 2001 ignore questions with an underlined number.

Revised: February 2001

Chapter 21: Electrochemistry 21-4.

Page 2

Consider an electrochemical cell where the following reaction takes place: 3 Sn 2+ (aq) + 2 Al(s) → 3 Sn(s) + 2 Al3+ (aq) Which of the following is the correct cell notation for this cell?

21-5.

(a)

Al | Al 3+ || Sn2+ | Sn

(b)

Al3+ | Al || Sn | Sn2+

(c)

Sn | Sn2+ || Al 3+ | Al

(d)

Sn | Al3+ || Al | Sn2+

Eo for the following redox reaction is +1.05 V. 2 Ag+ (aq) + Ni(s) → 2 Ag(s) + Ni2+ (aq) What is ∆Go for this reaction?

21-6.

(a)

+203 kJ

(b)

-203 kJ

(c)

+101 kJ

(d)

-101 kJ

Eo for the following redox reaction is -0.029 V. Fe3+ (aq) + 3 Ag(s) → Fe 2+ (aq) + 3 Ag + (aq) What is ∆Go for this reaction?

21-7.

(a)

+2.8 kJ

(b)

-2.8 kJ

(c)

+8.4 kJ

(d)

-8.4 kJ

An early method of producing aluminum metal was the reaction of aluminum salts with sodium metal: Al3+ + 3 Na(s) → Al(s) + 3 Na+

Eo = +1.05 V

What is ∆Go for this reaction?

21-8.

(a)

-304 kJ

(b)

+101 kJ

(c)

-101 kJ

(d)

+304 kJ

The following redox reaction can be used to form iodine. Br2(aq) + 2 I - (aq) → 2 Br - (aq) + I2(aq)

∆Go = -105 kJ

What is E o for this reaction? (a)

+1.09 V

(b)

-1.09 V

(c)

+0.0011 V

(d)

+0.545 V



21-10.

Page 3

The following reaction can be used to form bromine. Cl 2(aq) + 2 Br- (aq) → 2 Cl - (aq) + Br2(aq)

∆Go = -102 kJ

(a)

+1.06 V

(b)

-1.06 V

(c)

+0.53 V

(d)

-0.53 V

It would be useful if a battery could be made utilizing the following reaction: 2 Li(s) + F2(g) → 2 LiF(s)

∆Go = -1141 kJ

What is E o for this reaction?

21-11.

(a)

+11.8 V

(b)

-11.8 V

(c)

+2.7 V

(d)

+5.9 V

Given the two following half reactions, Ni2+ (aq) + 2e- → Ni(s)

Eo = -0.25 V

Hg2+ (aq) + 2e- → Hg(l)

Eo = +0.86 V

calculate Eo for the following reaction: Hg2+ (aq) + Ni(s) → Ni 2+ (aq) + Hg(l)

21-12.

(a)

-1.11 V

(b)

+0.61 V

(c)

+1.11 V

(d)

-0.61 V

Given the two following half reactions, Cu 2+ (aq) + 2e- → Cu(s)

Eo = +0.34 V

Hg2+ (aq) + 2e- → Hg(l)

Eo = +0.86 V

calculate Eo for the following reaction: Hg2+ (aq) + Cu(s) → Cu 2+ (aq) + Hg(l) (a)

-1.20 V

(b)

+0.52 V

(c)

+1.20 V

(d)

-0.52 V



Page 4

Given the two following half reactions, Mg2+ (aq) + 2e- → Mg(s) I2(aq)

+ 2e - → 2 I- (aq)

Eo = -2.37 V Eo = +0.54 V

calculate Eo for the following reaction: Mg2+ (aq) + 2 I - (aq) → I 2(aq) + Mg(s)

21-14.

(a)

-2.91 V

(b)

-1.83 V

(c)

+1.83 V

(d)

-2.91 V

Given the two following half reactions, Sn 2+ (aq) + 2e- → Sn(s)

Eo = -0.14 V

Sn 4+ (aq) + 2e- → Sn 2+ (aq)

Eo = +0.15 V

calculate Eo for the following reaction: Sn 4+ (aq) + Sn(s) → 2 Sn 2+ (aq)

21-15.

(a)

-0.01 V

(b)

-0.29 V

(c)

+0.29 V

(d)

+0.01 V

An electrochemical cell of notation Pd | Pd2+ || Cu2+ | Cu has Eo = -0.65 V. If we know that the standard reduction potential of Cu2+ /Cu is Eo = 0.34 V, what is the standard reduction potential for Pd2+ /Pd?

21-16.

(a)

-0.99 V

(b)

-0.31 V

(c)

+0.31 V

(d)

+0.99 V

An electrochemical cell of notation Pt | Pt2+ || Ni 2+ | Ni has Eo = -1.45 V. If we know that the standard reduction potential of Ni2+ /Ni is Eo = -0.25 V, what is the standard reduction potential for Pt2+ /Pt?

21-17.

(a)

+1.70 V

(b)

-1.20 V

(c)

+1.20 V

(d)

-1.70 V

Given the following two half reactions, Cd2+ (aq) + 2e- → Cd(s)

Eo = -0.40 V

Zr4+ (aq) + 4e- → Zr(s)

Eo = -1.53 V

determine Eo and the spontaneity of the following reaction 2 Cd2+ (aq) + Zr(s) → 2 Cd(s) + Zr4+ (aq) (a)

+1.13 V and not spontaneous

(b)

+1.13 V and spontaneous

(c)

-1.13 V and not spontaneous

(d)

-1.13 V and spontaneous



Page 5

Given the following two half reactions, Ca2+ (aq) + 2e- → Ca(s)

Eo = -2.87 V

V2+ (aq) + 2e- → V(s)

Eo = -1.21 V

determine Eo and the spontaneity of the following reaction Ca2+ (aq) + V(s) →> Ca(s) + V2+ (aq)

21-19.

(a)


(b)


(c)


(d)


Given the following two half reactions, Sr2+ (aq) + 2e- → Sr(s)

Eo = -2.89 V

Mn2+ (aq) + 2e- → Mn(s)

Eo = -1.18 V

determine Eo and the spontaneity of the following reaction Sr2+ (aq) + Mn(s) → Sr(s) + Mn2+ (aq) (a)


(b)


(c)


(d)


21-20. Given the following two half reactions, Sn 2+ (aq) + 2e- → Sn(s)

Eo = -0.14 V

I2 + 2e- → 2 I- (aq)

Eo = +0.54 V

determine Eo and the spontaneity of the following reaction Sn(s) + 2 I- (aq) → Sn 2+ (aq) + I2(aq)

21-21.

(a)


(b)


(c)


(d)

+2.39 V and not spontaneous

Determine the cell potential for Mg(s) + 2 Ag+ (aq) → Mg2+ (aq) + 2 Ag(s) where [Ag+ ] = 0.30 M and [Mg 2+ ] = 0.020 M using the following standard reduction potentials. Mg2+ (aq) + 2e- → Mg(s)

Eo = -2.37 V

Ag+ (aq) + e- → Ag(s)

Eo =+0.80 V

(a)

+3.14 V

(b)

-3.14 V

(c)

+1.60 V

(d)

+3.20 V



Page 6

Determine the cell potential for Ni(s) + Fe2+ (aq) → Ni 2+ (aq) + Fe(s) where [Ni2+ ] = 0.60 M and [Fe 2+ ] = 0.0030 M using the following standard reduction potentials.

21-23.

Ni2+ (aq) + 2e- → Ni(s)

Eo = -0.25 V

Fe2+ (aq) + 2e- → Fe(s)

Eo = -0.44 V

(a)

+0.76 V

(b)

-0.19 V

(c)

-0.26 V

(d)

-0.12 V

Determine the cell potential for Cu(s) + Pt2+ (aq) → Cu 2+ (aq) + Pt(s) where [Cu2+ ] = 0.85 M and [Pt2+ ] = 0.0070 M using the following standard reduction potentials.

21-24.

Pt 2+ (aq) + 2e- → Pt(s)

Eo = +1.20 V

Cu 2+ (aq) + 2e- → Cu(s)

Eo = +0.34 V

(a)

+0.80 V

(b)

-0.92 V

(c)

+1.60 V

(d)

+0.86 V

Determine the cell potential for Cu(s) + Ag+ (aq) → Cu + (aq) + Ag(s) where [Ag+ ] = 0.25 M and [Cu + ] = 0.00050 M using the following standard reduction potentials.

21-25.

Ag+ (aq) + e- → Ag(s)

Eo = +0.80 V

Cu + (aq) + e- → Cu(s)

Eo = +0.52 V

(a)

+0.44 V

(b)

+0.12 V

(c)

+0.28 V

(d)

-0.28 V

Determine the equilibrium constant for the following reaction at 25 oC. Cl 2(aq) + 2I - (aq) → 2 Cl - (aq) + I2(aq) Eo = +0.825 V (a)

1.08 x 10-28

(b)

0.825

(c)

9.25 x 1027

(d)

0.217



Page 7

Determine the equilibrium constant for the following reaction at 25 oC. Sn 2+ (aq) + V(s) → Sn(s) + V2+ (aq)

21-27.

Eo = +1.07 V

(a)

1.41 x 1036

(b)

7.10 x 10-27

(c)

-1.07

(d)

1.19 x 1018

Given the following two half reactions, Hg2+ (aq) + 2e- → Hg(l)

Eo = +0.79 V

Ni2+ (aq) + 2e- → Ni(s)

Eo = -0.25 V

determine the equilibrium constant for Hg(l ) + Ni2+ (aq) → Hg 2+ (aq) + Ni(s)

21-28.

(a)

1.75 x 1018

(b)

7.56 x 10-10

(c)

1.32 x 109

(d)

5.71 x 10-19

Given the following two half reactions, Al3+ (aq) + 3e- → Al(s)

Eo = -1.66 V

Cl 2(aq) + 2e- → 2 Cl - (aq)

Eo = +1.36 V

determine the equilibrium constant for 2 Al 3+ (aq) + 6 Cl- (aq) R 2 Al(s) + 3 Cl2(aq)

21-29.

21-30.

21-31.

(a)

10-306

(b)

10+306

(c)

10-51

(d)

10+51

How many coulombs of charge are required to deposit 1.00 g Ag from a solution of Ag+ (aq)? (a)

9.27 x 10-3

(b)

894

(c)

1790

(d)

1.00

How many coulombs of charge are required to form 1.00 pound of Al(s) from an Al3+ salt? (a)

4.87 x 106

(b)

50.5

(c)

106

(d)

454

1.62 x

If we wish to convert 1.00 g of Au3+ (aq) ion into Au(s) in a “gold-plating" process, how long must we electrolyze a solution if the current passing through the circuit is 2.00 amps? (a)

245 sec

(b)

0.50 sec

(c)

0.015 sec

(d)

735 sec



Page 8

If we electrolyze a solution of Ni2+ (aq) to form Ni(s) and use a current of 0.15 amps for 10 minutes, how many grams of Ni(s) are produced? (a) (c)

21-33.

0.027 g 4.56 x

10-4

g

(b)

0.054 g

(d)

5280 g

We have 100. mL of a solution of Cu2+ (aq) ion and wish to determine [Cu2+ ]. We electrolyze the solution to produce Cu(s) and use 1.5 amps of current for 1120 seconds to complete the process. What was the concentration of Cu2+ in the solution?

21-34.

(a)

0.174 M

(b)

0.871 M

(c)

0.0871 M

(d)

1.74 M

Assuming 100% efficiency, how many kilowatt hours (kwh) of electrical energy are required to produce 1.00 kg of chlorine gas by the following reaction: NaCl(aq) + H2O(l ) → NaOH(aq) + 1/2 Cl2(g) + 1/2 H2(g)

21-35.

Eo = -1.36 V

(a)

2.06 kwh

(b)

22.5 kwh

(c)

1.03 kwh

(d)

0.514 kwh

In the production of Al metal by electrolysis, approximately 15 kwh of electrical energy are used to produce each kilogram of Al from an Al 3+ . Assuming that all the charge passed is used in producing aluminum, at what voltage does the cell operate?

21-36.

(a)

2.51 V

(b)

15.1 V

(c)

1.68 V

(d)

5.03 V

How many kilowatt hours of electrical energy are required to plate 1.00 grams of gold from an Au3+ (aq) solution onto a piece of jewelry? Assume an operating voltage of 3.00 V is necessary.

21-37.

(a)

4.08 x 10-4 kwh

(b)

1.22 x 10-3 kwh

(c)

1.36 x 10-4 kwh

(d)

51.4 kwh

In reducing Ag+ ion for plating onto jewelry, an operating cell voltage of 4.00 V is required. If you run a business that does this kind of work, how much will the electrical energy cost to coat 1.0 x 104 necklaces with 0.10 g silver each? Assume that the cost of electricity is $0.10/kwh. (a)

26 cents

(b)

10. cents

(c)

$122

(d)

$14.56



Page 9

21-38. How is aluminum currently produced in industry?

21-39.

21-40.

21-41.

21-42.

(a)

by reduction of Al3+ in Al2O3 with Na(s)

(b)

electrochemical reduction of pure Al2O3 to give Al and O 2

(c)

electrolysis of AlF 3 to give Al and F2

(d)

electrolysis of a mixture of Al 2O3 and Na3AlF 6 to give Al and O 2

How is sodium currently produced in industry? (a)

by reduction of Na+ in NaCl with Al(s)

(b)

electrolysis of pure NaCl(l)

(c)

electrolysis of a molten mixture of NaCl and other salts

(d)

electrolysis of an aqueous solution of NaCl and other salts

The products obtained from electrolysis of brine (aqueous NaCl) are: (a)

HCl(g), Na(s) and O2(g)

(b)

H2(g), NaOH(aq), and Cl2(g)

(c)

Na(s) and Cl2(g)

(d)

NaOH(aq) and HCl(aq)

A possible anodic reaction that takes place during corrosion of iron is: (a)

O2(g) + 2 H2O(l) + 4e- → 4 OH - (aq)

(b)

Fe(s) → Fe 2+ + 2e-

(c)

2 H2O(l) + 2e- → H 2(g) + 2 OH- (aq)

(d)

SO2(g) + O2(g) + 2e- → SO 42- (aq)

Which of the following is NOT a possible cathodic reaction in the corrosion of iron? (a)

O2(g) + 2 H2O(l) + 4e- → 4 OH- (aq)

(b)

2 H2O(l) + 2e- → H 2(g) + 2 OH- (aq)

(c)

SO2(g) + O2(g) + 2e- → SO 42- (aq)

(d)

Fe(s) → Fe 2+ (aq) + 2e-



Page 10

Which of the following reactions does a common alkaline battery, such as those used in portable tape players, utilize?

21-44.

21-45.

(a)

Zn(s) + MgO(s) → ZnO(s) + Mg(s)

(b)

ZnO(s) + Mg(s) → Zn(s) + MgO(s)

(c)

2 Zn(s) + 2 MnO2(s) → 2 ZnO(s) + Mn2O3(s)

(d)

Zn(s) + HgO(s) → Hg(l) + ZnO(s)

Which of the following reactions does a lead-acid battery, such as that used in an automobile, utilize? (a)

PbO2(s) + H2SO4(aq) → Pb 2+ (aq) + H2(g) + SO42- (aq)

(b)

2 PbO 2(s) → Pb(s) + PbO4(s)

(c)

HCl(aq) + Pb(s) → H 2(g) + PbCl2(s)

(d)

Pb(s) + PbO2(s) + 2 H2SO4(aq) → 2 PbSO4 + 2 H 2O(l)

Given the following half-reactions, Ag+ (aq) + e- → Ag(s)

Eo = +0.799 V

AgCl(s) + e- → Ag(s) + Cl- (aq)

Eo = +0.222 V

calculate the molar solubility of AgCl.

21-46.

(a)

4.46 x 10-9 M

(b)

1.34 x 10-5 M

(c)

1.79 x 10-10 M

(d)

-0.577 M

Given the following half reactions, Cd2+ (aq) + 2e- → Cd(s)

Eo = -0.403 V

CdS(s) + 2e- → Cd(s) + S2- (aq)

Eo = -1.21 V

estimate the molar solubility of CdS. (a)

2.33 x 10-14 M

(b)

5.43 x 10-28 M

(c)

1.84 x 1027 M

(d)

4.29 x 1013 M



Page 11

An electrochemical cell is constructed with two iron electrodes. The solution in the left hand compartment of the cell has 1.0 M Fe2+ (aq) while the solution in the right hand compartment contains 0.10 M Fe2+ (aq). Which of the following is true about the cell?

21-48.

(a)

no current flows through the wire connecting the electrodes

(b)

both electrodes are oxidized

(c)

reduction occurs in the left hand compartment

(d)

reduction occurs in the right hand compartment

An electrochemical cell is constructed with two inert electrodes that transfer electrons but are not oxidized or reduced. In the left hand compartment of the cell is a solution containing 0.10 M Cl2(aq) and 0.50 M Cl - (aq). In the right hand compartment of the cell is a solution containing 0.50 M Cl2(aq) and 0.50 M Cl - (aq). Which of the following is true about the cell?

21-49.

(a)

no current flows through the wire connecting the electrodes

(b)

both electrodes are oxidized

(c)

reduction occurs in the left hand compartment

(d)

reduction occurs in the right hand compartment

An electrochemical cell is constructed with two Ni(s) electrodes, each in a cell containing Ni2+ (aq). Electrons flow through the wire connecting the electrodes from the left hand compartment to the right hand compartment. What can be said about the overall cell? (a)

[Ni2+ ] in the right compartment > [Ni2+ ] left compartment

(b)

[Ni2+ ] in the right compartment < [Ni2+ ] left compartment

(c)

no magnetic fields penetrate the walls of the cell

(d)

Ni2+ (aq) is more easily oxidized than Ni(s)



Page 12

We have a sample of an unknown metal that we know can be oxidized by one electron. We wish to determine which element we have. Which of the following would be a possible means of determining which element we have? (a)

construct an electrochemical cell and measure Eo of the metal, and compare it to a table of potentials

(b)

determine if the metal oxidizes Fe2+ → Fe 3+

(c)

construct an electrochemical cell and measure how quickly current passes from compartment to compartment

(d)

21-51.

determine if the metal heats up when it is oxidized

Consider the following half reactions: HALF REACTION

E˚(V)

F 2(g) + 2 e- → 2 F - (aq)

+2.87

I2(g) + 2 e- → 2I- (aq)

+0.56

Cu 2+ (aq) + 2 e- → Cu(s)

+0.34

Al3+ (aq) + 3 e- → Al(s)

-1.66

(i)

Which is the strongest oxidizing agent?

________________

(ii)

Which is the strongest reducing agent?

________________

(iii)

Will Al(s) reduce Cu2+ (aq) to Cu(s)?

________________

(iv)

Will

F- (aq) reduce I2(aq) to I- (g)?

________________

(v)

Name the elements or ions that can be reduced by Cu(s).

(vi)

/I-

If you build a battery using the I 2

and

Al3+ /Al

half reactions, what is the voltage of the battery

(assuming all reagents are at standard conditions)? (a)

+1.66 V

(b)

+0.56 V

(c)

+2.20 V

(d)

-2.20 V


________________


21-53.

Page 13

Consider the following half reactions: HALF REACTION

E˚(V)

Cl 2(g) + 2 e- → 2 Cl - (aq)

+1.36

I2(g) + 2 e- → 2I- (aq)

+0.535

Pb 2+ (aq) + 2 e- → Pb(s)

-0.126

e-

→ V(s)

V2+ (aq)

+2

(i)

Which is the weakest oxidizing agent in the list?

________________

(ii)

Which is the strongest oxidizing agent?

________________

(iii)

Which is the strongest reducing agent?

________________

(iv)

Which is the weakest reducing agent?

________________

(v)

Will I - (aq) reduce Cl2(aq) to Cl- (g)?

________________

(vi)

Name the elements or ions that can be reduced by Pb(s).

-1.18

________________

The basic reaction occurring in the cell in which Al2O3 and aluminum salts are electrolyzed is Al3+ + 3 e→ Al(s). If the cell operates at 5.0 V and 1.0 x 105 amps, and you want to produce 600 pounds of aluminum metal (2.7 x 105 g), how many hours will you need to operate the cell?

21-54.

(a)

1.0 hour

(b)

4.0 hours

(c)

8.0 hours

(d)

24.0 hours

The space shuttle uses fuel cells for electricity, and one cell that has been proposed is based on hydrazine, N2H4, and O2. The reactions are (a)

N2H4(aq) + 4 OH- (aq) → N 2(g) + 4 H2O(l) + 4 e-

(b)

O2(g) + 2 H2O(l ) + 4 e- → 4 OH- (aq)

(i)

Which reaction occurs at the anode? ______

(ii)

If the cell is to produce 0.50 amps of current for 50.0 hours, how many grams of hydrazine (N 2H4) must be present? (1 Faraday = 96,500 coulombs/mol e - ) (a)

7.5 g

(b)

29.9 g

(c)

3.25 g

(d)

0.0021 g



Page 14

Imagine an electrochemical cell using the setup below. Voltmeter

Ni

Cu salt bridge

1 M Ni

2+

2+

1 M Cu

Ni2+ (aq) + 2e- → Ni(s)

E˚ = -0.25 V

Cu 2+ (aq) + 2e- → Cu(s) (i)

(ii)

(iii)

Write a balanced equation depicting the reaction occurring in the cell above and give its E˚ value. (a)

Ni2+ (aq) + Cu(s) → Cu 2+ (aq) + Ni(s)

E˚ = -0.59 V

(b)

Cu 2+ (aq) + Ni(s) → Ni 2+ (aq) + Cu(s)

E˚ = +0.59 V

(c)

Cu 2+ (aq) + Ni(s) → Ni 2+ (aq) + Cu(s)

E˚ = -0.59 V

(d)

Ni2+ (aq)

+ Ni(s)

E˚ = +0.59 V

(a)

Ni2+ (aq)

(b)

Cu 2+ (aq)

(c)

Ni(s)

(d)

Cu(s)

(b)

Cu

(b)

negative

Which is the anode? Ni

What is the polarity of the Cu electrode? (a)

(v)

+ Cu(s) →

Cu 2+ (aq)

What is oxidized?

(a) (iv)

E˚ = +0.34 V

positive

What is the direction of electron flow in the external wire? (a)


from Cu to Ni

(b)

from Ni to Cu


Page 15

Ni-cad batteries are rechargeable and are commonly used in cordless appliances. Although such batteries actually function under basic conditions, imagine an electrochemical cell using the setup below. Voltmeter

Cd

Ni salt bridge

1 M Cd

(i)

(ii)

1 M Ni

2+

Cd2+(aq) + 2e- → Cd(s)

E˚ = -0.40 V

Ni2+ (aq) + 2e- → Ni(s)

E˚ = -0.25 V

What is E˚ for the cell? (a)

-0.15 V

(b)

+0.15 V

(c)

+0.65 V

(d)

+0.40 V

(b)

Ni

Which is the cathode? (a)

(iii)

2+

Cd

Which statement below is true? (a)

Electrons flow from Cd to Ni in the external wire, and NO3- ions in the salt bridge move toward the Ni2+ /Ni compartment.

(b)

Electrons flow from Cd to Ni in the external wire, and NO3- ions in the salt bridge move toward the Cd2+ /Cd compartment.

(c)

Electrons flow from Ni to Cd in the external wire, and NO3- ions in the salt bridge move toward the Ni2+ /Ni compartment.

(iv)

If 0.050 amps are drawn from the battery, how long can it last if you begin with 100. mL of each of the solutions and each was initially 0.10 M in dissolved species? The electrodes each weigh 50.0 g in the beginning. (a)

5.36 hours

(b)

10.7 hours

(c)

107 hours

(d)

477 hours



Page 16 ANSWERS — CHAPTER 21

1.

b

11.

c

21.

d

2.

b

12.

b

22.

c

3.

c

13.

d

23.

a

4.

a

14.

c

24.

a

5.

b

15.

d

25.

c

6.

c

16.

c

26.

a

7.

a

17.

b

27.

d

8.

d

18.

b

28.

a

9.

c

19.

c

29.

b

10.

d

20.

a

30.

a

31.

d

41.

b

32.

a

42.

d

33.

c

43.

c

34.

c

44.

d

35.

d

45.

b

36.

b

46.

a

37.

b

47.

c

38.

d

48.

d

39.

c

49.

a

40.

b

50.

a

51.

F 2, Al, yes, no, F 2 and I2, c

52.

V2+ , Cl 2, V, Cl - , yes, I2 and Cl2

53.

c

54.

a, a

55.

b, c, a, a, b

56.

b, b, b, b


Chapter 18 BANK

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