Electrochemical Cell Examples: 44 Problems with Answers

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Electrochemical Cell.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

An electrochemical cell is a system with two half-reactions separated into electrodes and connected through an external circuit so electrons can flow.

Separate the oxidation and reduction halves, connect them with a wire and ion path, and the reaction can do electrical work.

Read the full concept explanation →

How to Use These Examples

Read the first worked example with the solution open so the structure is clear.
Try the practice problems before revealing each solution.
Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Electrochemical Cell starts by assigning oxidation and reduction, then traces electrons through the wire and ions through solution.

Common stuck point: Students often know a formula related to electrochemical cell but skip the recognition step: Am I tracking oxidation, reduction, electron flow, ions, electrodes, and whether the cell is spontaneous or driven? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Am I tracking oxidation, reduction, electron flow, ions, electrodes, and whether the cell is spontaneous or driven?

Worked Examples

Example 1

medium

An electrochemical cell uses

Sn^{2+}/Sn

(

-0.14\text{ V}

) and

Cu^{2+}/Cu

(

+0.34\text{ V}

). Identify the anode, cathode, electron flow, and

E^\circ_{cell}

Answer

{Anode: Sn; Cathode: Cu; e}^{-} : Sn \to Cu; E_{c e l l}^{\circ} = + 0.48 V

First step

More positive

E^\circ

wins reduction: Cu is cathode.

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Example 2

medium

A galvanic cell delivers a steady current of

0.50\text{ A}

for

193\text{ s}

. How many moles of electrons pass through the external circuit? (

F = 96500\text{ C/mol}

)

Example 3

medium

An electrochemical cell with

Cu|Cu^{2+}(1\text{ M})||Ag^+(1\text{ M})|Ag

runs. Half-reactions:

Cu^{2+}+2e^- \to Cu

(

+0.34\text{ V}

) and

Ag^+ + e^- \to Ag

(

+0.80\text{ V}

). Write the overall reaction.

Example 4

hard

An electrochemical cell uses

Cr^{3+}/Cr

(

-0.74\text{ V}

) and

Fe^{2+}/Fe

(

-0.44\text{ V}

). Determine the spontaneous direction and find

E^\circ_{cell}

Example 5

hard

An electrochemical cell with

Zn|Zn^{2+}(0.10\text{ M})||Cu^{2+}(1.0\text{ M})|Cu

has

E^\circ_{cell} = +1.10\text{ V}

. Use the Nernst equation to find

E_{cell}

25\,^{\circ}\text{C}

(

n=2

Example 6

hard

An electrochemical cell uses standard hydrogen electrode (SHE,

0.00\text{ V}

) as cathode and

Zn^{2+}/Zn

(

-0.76\text{ V}

) as anode. Find

E^\circ_{cell}

and the spontaneous direction.

Example 7

challenge

An electrochemical cell uses

Mg|Mg^{2+}(1\text{ M})||Ag^+(1\text{ M})|Ag

. Given

E^\circ(Mg^{2+}/Mg) = -2.37\text{ V}

and

E^\circ(Ag^+/Ag) = +0.80\text{ V}

, compute

E^\circ_{cell}

, the moles of electrons per mole of Mg, the balanced overall equation, and

\Delta G^\circ

. (

F = 96500\text{ C/mol}

)

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy

What are the two electrodes in an electrochemical cell called?

Example 2

easy

In an electrochemical cell, what flows through the external wire?

Example 3

easy

Does oxidation occur at the anode or cathode of an electrochemical cell?

Example 4

easy

What flows through the salt bridge of an electrochemical cell?

Example 5

easy

Reduction occurs at which electrode of an electrochemical cell?

Example 6

easy

In a galvanic cell, electrons flow from the anode to the ___.

Example 7

easy

Why does an electrochemical cell separate the two half-reactions?

Example 8

easy

In the Daniell cell, the copper electrode is the cathode. Is copper reduced or oxidized?

Example 9

medium

A cell pairs

Zn \rightarrow Zn^{2+} + 2e^-

and

Cu^{2+} + 2e^- \rightarrow Cu

. Write the overall reaction.

Example 10

medium

If the anode metal dissolves and the cathode metal plates out, where does the cell gain mass?

Example 11

medium

In a galvanic cell, which direction do anions migrate in the salt bridge?

Example 12

medium

A cell notation is written

Zn|Zn^{2+}||Cu^{2+}|Cu

. Which side is the anode?

Example 13

medium

Why must a salt bridge be present for a galvanic cell to keep working?

Example 14

medium

In a cell, oxidation half is

Fe \rightarrow Fe^{2+} + 2e^-

and reduction is

Ag^+ + e^- \rightarrow Ag

. Balance the overall reaction.

Example 15

medium

A galvanic cell and an electrolytic cell both label oxidation at the anode. What differs about their energy?

Example 16

medium

In a galvanic cell, which direction do cations migrate in the salt bridge?

Example 17

medium

In the cell notation

Zn|Zn^{2+}||Cu^{2+}|Cu

, which side is the cathode?

Example 18

challenge

Given

Ag^+ + e^- \rightarrow Ag

(

+0.80

V) and

Cu^{2+} + 2e^- \rightarrow Cu

(

+0.34

V), determine the cathode and

E^\circ_{cell}

Example 19

challenge

In a

Zn/Cu

cell with

E^\circ_{cell}=1.10

V, 0.50 mol of electrons pass. Find the maximum electrical work. (F = 96500 C/mol)

Example 20

challenge

A cell uses half-reactions with

E^\circ

values +0.34 V (Cu) and -0.76 V (Zn). If you reverse the cell to make it electrolytic, what minimum voltage must be applied?

Example 21

easy

An electrochemical cell uses

Mg \to Mg^{2+} + 2e^-

at one electrode. Is this the anode or the cathode?

Example 22

easy

In an electrochemical cell with

Ni|Ni^{2+}||Ag^+|Ag

, identify the cathode.

Example 23

easy

An electrochemical cell uses

Pb^{2+} + 2e^- \to Pb

at one electrode. Identify the role of that electrode.

Example 24

easy

If a galvanic cell runs spontaneously, is

E^\circ_{cell}

positive or negative?

Example 25

medium

An electrochemical cell pairs

Mg|Mg^{2+}||Cu^{2+}|Cu

. Given

E^\circ(Mg^{2+}/Mg) = -2.37\text{ V}

and

E^\circ(Cu^{2+}/Cu) = +0.34\text{ V}

, find

E^\circ_{cell}

Example 26

medium

In an electrochemical cell with

Al|Al^{3+}||Cu^{2+}|Cu

, write the overall balanced reaction.

Example 27

medium

In a galvanic cell, which direction do cations from the salt bridge migrate, and why?

Example 28

medium

An electrochemical cell with a Zn anode in

Zn^{2+}

solution drives a current. As it runs, what happens to

[Zn^{2+}]

in the anode half-cell?

Example 29

medium

An electrochemical cell uses

Fe^{3+}/Fe^{2+}

(

+0.77\text{ V}

) and

Sn^{4+}/Sn^{2+}

(

+0.15\text{ V}

). Which half-reaction is the oxidation?

Example 30

medium

In an electrochemical cell, the salt bridge contains

KNO_3

. Which ion moves toward the cathode?

Example 31

medium

For an electrochemical cell with

E^\circ_{cell} = +0.46\text{ V}

and

n = 2

, compute

\Delta G^\circ

in kJ. (

F = 96500\text{ C/mol}

)

Example 32

medium

Write the standard cell notation for the spontaneous reaction

Zn + Ni^{2+} \rightarrow Zn^{2+} + Ni

Example 33

hard

A current of

1.50\text{ A}

flows for

600\text{ s}

through an electrochemical cell electroplating Ag from

Ag^+

. Find the mass of Ag deposited. (

F = 96500\text{ C/mol}

M(Ag) = 108\text{ g/mol}

)

Example 34

hard

A student claims that in a galvanic cell, electrons travel through the salt bridge to complete the circuit. Identify the error and give the correction.

Example 35

hard

An electrochemical cell uses two iron electrodes in

Fe^{2+}

solutions of different concentrations: anode at

0.010\text{ M}

, cathode at

1.0\text{ M}

. Find

E_{cell}

25\,^{\circ}\text{C}

(

n=2

Example 36

hard

An electrolytic cell electrolyzes molten

AlCl_3

. Find the mass of Al produced by

9650\text{ C}

of charge. (

M(Al)=27\text{ g/mol}

F=96500\text{ C/mol}

)

Example 37

hard

In a galvanic cell, the cathode metal increases in mass by

0.635\text{ g}

(Cu). How many coulombs flowed? (

M(Cu)=63.5\text{ g/mol}

F=96500\text{ C/mol}

)

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Related Concepts

Electrochemistry Electrolytic Cell

Background Knowledge

These ideas may be useful before you work through the harder examples.

electrochemistry