Electrochemistry Examples in Chemistry

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

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

Concept Recap

Electrochemistry is the study of redox reactions that involve electric current, either producing electricity from a spontaneous reaction (a galvanic/voltaic cell) or using electricity to force a nonspontaneous reaction to occur (an electrolytic cell).

Electrochemistry connects chemical reactions and electrical energy in both directions.

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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: Electrochemistry 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 electrochemistry 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

A current of

2.00\text{ A}

runs for

1\,930\text{ s}

in an electrolysis of aqueous

CuSO_4

. Find the mass of Cu deposited. (

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

F=96500\text{ C/mol}

)

Answer

\text{Mass} \approx 1.27\text{ g Cu}

First step

Q = It = 2.00 \cdot 1930 = 3860\text{ C}

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Example 2

medium

Two electrolysis cells are wired in series: one plates Ag (

Ag^+ + e^- \to Ag

), the other plates Cu (

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

). If

0.10\text{ mol}

Ag is deposited, how many moles of Cu form?

Example 3

medium

An aqueous

NaCl

electrolysis at the cathode reduces water rather than

Na^+

. Explain why, citing reduction potentials.

Example 4

hard

Use the Nernst equation at

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

: a cell has

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

with

n = 2

and

Q = 100

. Find

E_{cell}

Example 5

hard

For the Daniell cell

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

n = 2

. Compute the equilibrium constant

K

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

Example 6

hard

An electrolytic cell electroplates

Cr

from

Cr^{3+}

10.0\text{ A}

. How long to plate

5.20\text{ g}

of Cr? (

M(Cr)=52.0

F=96500\text{ C/mol}

)

Example 7

challenge

An electrochemical cell at

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

has

E^\circ_{cell} = +0.20\text{ V}

with

n = 2

. The cell is discharged until

E_{cell} = +0.10\text{ V}

. What is

Q

at that moment?

Practice Problems

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

Example 1

easy

Electrochemistry studies redox reactions involving what form of energy?

Example 2

easy

In a spontaneous electrochemical cell, electrons flow from which electrode to which?

Example 3

easy

Does a spontaneous redox reaction produce or consume electrical energy?

Example 4

easy

At which electrode does oxidation occur?

Example 5

easy

In an electrochemical cell, what carries charge through the solution?

Example 6

easy

Does electrolysis use a spontaneous or nonspontaneous reaction?

Example 7

easy

Which device converts chemical energy into electrical energy: a battery or an electrolysis cell?

Example 8

easy

What component allows ion flow between half-cells while keeping solutions separate?

Example 9

medium

A cell has

E^\circ_{cell} = +1.10

V. Is the reaction spontaneous, and is the cell galvanic?

Example 10

medium

For

E^\circ_{cell} = +0.46

V with

n=2

, find the sign of

\Delta G

using

\Delta G = -nFE^\circ_{cell}

Example 11

medium

In the Zn/Cu cell, Zn is oxidized and Cu2+ is reduced. Which metal is the anode?

Example 12

medium

If electrons flow from electrode A to electrode B in the wire, which is the cathode?

Example 13

medium

A galvanic cell powers a circuit. As it runs, does the anode gain or lose mass (for a metal anode like Zn)?

Example 14

medium

During electrolysis of molten

NaCl

, at which electrode is

Na

metal produced?

Example 15

medium

Which has a higher (more positive) cell potential trend: a cell with a large positive

\Delta G

or a large negative

\Delta G

Example 16

medium

In the Zn/Cu cell, Cu2+ is reduced at the copper electrode. Which electrode is the cathode?

Example 17

medium

A cell has

E^\circ_{cell} = -0.40

V. Is the reaction as written spontaneous?

Example 18

challenge

Given half-reactions

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

(

+0.34

V) and

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

(

-0.76

V), find

E^\circ_{cell}

for the spontaneous cell.

Example 19

challenge

A current of 2.0 A flows for 965 s in an electrolysis depositing

Cu

from

Cu^{2+}

. How many moles of Cu deposit? (F = 96500 C/mol)

Example 20

challenge

A galvanic cell has

E^\circ_{cell}=+1.10

V with

n=2

. Compute

\Delta G^\circ

in kJ. (F = 96500 C/mol)

Example 21

easy

Is corrosion of iron an example of electrochemistry?

Example 22

easy

Which of these is best classified as electrolysis: charging a phone, a rusting nail, a Zn/Cu cell powering a light?

Example 23

easy

Identify the oxidized and reduced species in:

Zn + Cu^{2+} \to Zn^{2+} + Cu

Example 24

easy

Which has the higher reduction potential:

F_2/F^-

(

+2.87

V) or

Li^+/Li

(

-3.04

V)? Which is the better oxidizing agent?

Example 25

medium

A cell has

E^\circ_{cell} = +0.92\text{ V}

with

n=2

. Compute

\Delta G^\circ

in kJ. (

F = 96500\text{ C/mol}

)

Example 26

medium

Convert: a cell delivers

96\,500\text{ C}

. How many moles of electrons? How many moles of Ag are deposited from

Ag^+

Example 27

medium

Use

\Delta G^\circ = -nFE^\circ_{cell}

: a galvanic cell has

\Delta G^\circ = -386\text{ kJ}

and

n = 4

. Find

E^\circ_{cell}

. (

F = 96500\text{ C/mol}

)

Example 28

medium

In an electrochemical cell at equilibrium, what is the value of

E_{cell}

Example 29

medium

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

E^\circ(Pb^{2+}/Pb) = -0.13

V. Which metal is the better reducing agent?

Example 30

medium

Why are noble gases generally inert in electrochemistry?

Example 31

medium

In an aluminum smelter (

Hall

Héroult

), molten alumina is electrolyzed. Where does the Al metal collect: anode or cathode?

Example 32

medium

A galvanic cell with

E^\circ_{cell} = +0.50\text{ V}

runs at

1.0\text{ A}

for

1.0\text{ hour}

. Find the electrical energy delivered.

Example 33

hard

A current of

5.0\text{ A}

deposits Ni from

Ni^{2+}

for

3860\text{ s}

. What mass of Ni is plated? (

M(Ni)=58.7

F=96500\text{ C/mol}

)

Example 34

hard

A student claims electrolysis can run without an external power source. Correct the misconception.

Example 35

hard

A fuel cell uses

H_2 + \tfrac{1}{2}O_2 \to H_2O

E^\circ_{cell} = +1.23\text{ V}

n = 2

. Compute the maximum electrical work per mole of

H_2

. (

F=96500\text{ C/mol}

)

Example 36

hard

A solution contains

Cu^{2+}

Ag^+

, and

Zn^{2+}

all at

1\text{ M}

. As an electrolysis is run at low voltage, which metal plates out first at the cathode?

Example 37

hard

A galvanic cell uses

H_2|H^+(1\text{ M})||Cu^{2+}(1\text{ M})|Cu

. Find

E^\circ_{cell}

given

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

and SHE =

0.00\text{ V}

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Related Concepts

Redox Reaction Electrolyte Electrochemical Cell Electrolytic Cell

Background Knowledge

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

redoxelectrolyte