Single Displacement Examples: 47 Problems with Answers

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

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

Concept Recap

A reaction in which one element replaces another in a compound, following the pattern $A + BC \rightarrow AC + B$ (or $A + BC \rightarrow BA + C$ , depending on which element is displaced).

A bully element kicks a weaker one out of its compound — like a stronger player replacing a weaker one on a team.

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: Single Displacement starts by comparing the reactant-product pattern, charges, states, and conserved atoms.

Common stuck point: Students often know a formula related to single displacement but skip the recognition step: Does the balanced equation match a recognizable pattern of reactants, products, ions, oxygen, or electron transfer? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Does the balanced equation match a recognizable pattern of reactants, products, ions, oxygen, or electron transfer?

Worked Examples

Example 1

easy

Write the balanced equation for zinc metal reacting with hydrochloric acid.

Zinc displacing hydrogen from hydrochloric acid

Answer

Zn + 2 HCl \to {ZnCl}_{2} + H_{2}

First step

Single displacement: a more reactive element replaces a less reactive one:

\text{A} + \text{BC} \rightarrow \text{AC} + \text{B}

Full solution

2
Zinc displaces hydrogen: $\text{Zn} + \text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2$ (unbalanced).
3
Balanced: $\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2$ . Check: Zn 1=1, H 2=2, Cl 2=2. ✓

In single displacement reactions, the activity series predicts whether the reaction will occur. Zinc is above hydrogen in the series, so it can displace hydrogen from the acid.

Example 2

medium

Will copper react with silver nitrate solution? If so, write the balanced equation. (Activity series: Cu is above Ag.)

Example 3

medium

Predict and balance:

\text{Al} + \text{Pb(NO}_3)_2 \rightarrow

? (Al > Pb)

Predict and balance: Al + Pb(NO₃)₂ → ? (Al > Pb)

Example 4

medium

Predict and balance:

\text{F}_2 + \text{NaBr} \rightarrow

? (F more reactive than Br)

Example 5

medium

Balance:

\text{Al} + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2

Balance: Al + H₂SO₄ → Al₂(SO₄)₃ + H₂

Practice Problems

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

Example 1

easy

Will gold (Au) react with

\text{CuSO}_4

solution? (Au is below Cu in the activity series.)

Example 2

hard

Zinc metal is placed in a copper(II) sulfate solution (

\text{CuSO}_4

). The solution gradually loses its blue color and a reddish deposit forms. Write the balanced equation and explain what the color changes indicate.

Example 3

easy

Classify:

Zn + 2HCl \rightarrow ZnCl_2 + H_2

. What reaction type?

Example 4

easy

Will

Cu

displace

Ag

AgNO_3

? (Cu is more reactive than Ag)

Example 5

easy

Complete:

Fe + CuSO_4 \rightarrow

? (Fe more reactive than Cu)

Example 6

easy

Which is single displacement? (a)

AgNO_3 + NaCl \rightarrow AgCl + NaNO_3

(b)

Mg + 2HCl \rightarrow MgCl_2 + H_2

Example 7

easy

A more reactive halogen displaces a less reactive one. Will

Cl_2 + 2NaBr \rightarrow

react? (Cl > Br)

Example 8

easy

A free element reacts with a compound, freeing one element. Name the type.

Example 9

easy

Will

Ag + CuSO_4

react? (Ag less reactive than Cu)

Example 10

easy

Complete:

2K + 2H_2O \rightarrow

? (K displaces H)

Example 11

medium

Balance:

Al + HCl \rightarrow AlCl_3 + H_2

Balance: Al + HCl → AlCl₃ + H₂

Example 12

medium

Predict and balance:

Zn + AgNO_3 \rightarrow

? (Zn > Ag, Zn is +2)

Example 13

medium

Will

Br_2 + 2NaCl \rightarrow

react? (Cl more reactive than Br)

Example 14

medium

Balance:

Mg + Fe_2O_3 \rightarrow MgO + Fe

Balance: Mg + Fe₂O₃ → MgO + Fe

Example 15

medium

Classify and explain:

Cl_2 + 2KI \rightarrow 2KCl + I_2

Example 16

medium

Identify the free element being displaced:

Fe + CuSO_4 \rightarrow FeSO_4 + Cu

Example 17

medium

Why does

Zn + CuSO_4

react but

Cu + ZnSO_4

does not?

Example 18

medium

Balance:

Na + H_2O \rightarrow NaOH + H_2

Balance: Na + H₂O → NaOH + H₂

Example 19

medium

Predict and balance:

Cl_2 + 2NaBr \rightarrow

? (Cl more reactive than Br)

Example 20

challenge

0.65 g Zn (M=65) reacts with excess HCl. Volume of

H_2

at STP (22.4 L/mol)?

Example 21

challenge

Excess Al reacts with 0.30 mol

CuCl_2

. Mol Cu produced? (

2Al + 3CuCl_2 \rightarrow 2AlCl_3 + 3Cu

)

Example 22

challenge

A 5.6 g iron nail (M=56) fully displaces Cu from

CuSO_4

. Mass of Cu (M=64) deposited?

Example 23

easy

Classify:

\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2

Example 24

easy

Will

\text{Mg} + \text{ZnCl}_2

react? (Mg is above Zn in the activity series.)

Example 25

easy

Complete:

\text{Zn} + 2\text{HCl} \rightarrow

Example 26

easy

Which is NOT single displacement? (a)

\text{Mg} + \text{CuSO}_4

; (b)

\text{NaCl} + \text{AgNO}_3

Example 27

medium

Balance:

\text{Ca} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 + \text{H}_2

Balance: Ca + H₂O → Ca(OH)₂ + H₂

Example 28

medium

Why doesn't gold react with HCl? Refer to the activity series.

Example 29

medium

Will

\text{I}_2 + \text{NaCl} \rightarrow

react? (I less reactive than Cl)

Example 30

medium

Balance:

\text{Fe} + \text{AgNO}_3 \rightarrow \text{Fe(NO}_3)_3 + \text{Ag}

Example 31

medium

\text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu}

, which species is oxidized?

Example 32

medium

In single displacement of an acid by a metal, what gas is typically produced?

Example 33

medium

In the activity series, why is potassium above sodium?

Example 34

medium

Predict the product when

\text{Br}_2

is added to

\text{KI}

solution.

Example 35

medium

3\text{Mg} + 2\text{AlCl}_3 \rightarrow 3\text{MgCl}_2 + 2\text{Al}

, what does this say about the activity series of Mg vs Al?

Example 36

hard

3.24 g Al (M=27) reacts with excess HCl. Find the moles of H

_2

produced. (

2\text{Al} + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2

)

Example 37

hard

Find the volume of H

_2

at STP (22.4 L/mol) produced from 1.30 g Zn (M=65) and excess HCl.

Example 38

hard

A 6.5 g iron sample (M=56) is placed in excess CuSO

_4

solution. Find the mass of Cu (M=64) deposited. (

\text{Fe} + \text{CuSO}_4 \rightarrow \text{FeSO}_4 + \text{Cu}

)

Example 39

hard

2.7

g Al reacts with excess CuSO

_4

. How many grams of Cu (M=64) are produced? (

2\text{Al} + 3\text{CuSO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{Cu}

, M

_\text{Al}

=27)

Example 40

hard

What single displacement reaction explains why zinc-coated nails (galvanized) protect iron from rusting?

Example 41

hard

Predict whether

\text{Cu} + 2\text{AgNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{Ag}

proceeds, and balance.

Example 42

challenge

A 4.8 g Mg strip (M=24) is added to 100 mL of 1.0 M CuSO

_4

. Identify the limiting reactant and find grams of Cu (M=64) produced.

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Related Concepts

Chemical Reaction Double Displacement

Background Knowledge

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

chemical reaction