Precipitation Reaction Examples: 44 Problems with Answers

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

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 type of double displacement reaction in which two aqueous ionic solutions are mixed and the exchange of ions produces at least one insoluble ionic compound (a precipitate) that drops out of solution as a solid.

Mix two clear solutions and a solid appears 'out of nowhere' — the ions combine to form a compound that won't dissolve.

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

Common stuck point: Students often know a formula related to precipitation reaction 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

Define a precipitation reaction. When solutions of

\text{AgNO}_3

and

\text{NaCl}

are mixed, a white solid forms. Identify the precipitate and write the balanced equation.

Silver nitrate and sodium chloride react to form white AgCl precipitate

Answer

{AgNO}_{3} + NaCl \to AgCl ↓ + {NaNO}_{3}

First step

A precipitation reaction occurs when two aqueous solutions are mixed and an insoluble solid (precipitate) forms.

Full solution

2
Exchange the cations: $\text{Ag}^+$ pairs with $\text{Cl}^-$ to form $\text{AgCl}$ , and $\text{Na}^+$ pairs with $\text{NO}_3^-$ to form $\text{NaNO}_3$ .
3
AgCl is insoluble (per solubility rules) and precipitates out. Balanced equation: $\text{AgNO}_3\text{(aq)} + \text{NaCl(aq)} \rightarrow \text{AgCl(s)}\downarrow + \text{NaNO}_3\text{(aq)}$ .

Precipitation reactions are a type of double displacement reaction driven by the formation of an insoluble product. Solubility rules help predict which ionic compounds are insoluble and will precipitate.

Example 2

medium

Predict whether a precipitate forms when solutions of

\text{Pb(NO}_3)_2

and

\text{KI}

are mixed. If so, identify the precipitate and write the balanced equation. Use solubility rules: most iodides are soluble, but

\text{PbI}_2

is insoluble.

Lead nitrate reacts with potassium iodide to form yellow PbI₂ precipitate

Example 3

medium

Write the net ionic equation for

\text{AgNO}_3\text{(aq)} + \text{NaCl(aq)} \rightarrow \text{AgCl(s)} + \text{NaNO}_3\text{(aq)}

Example 4

medium

How many grams of AgCl form when

50.0\,\text{mL}

0.200\,\text{M}

AgNO

_3

reacts with excess NaCl? (

M_\text{AgCl} = 143.32\,\text{g/mol}

Example 5

medium

What volume of

0.100\,\text{M}

AgNO

_3

is needed to precipitate all the chloride in

25.0\,\text{mL}

0.0500\,\text{M}

NaCl?

Example 6

hard

100.0\,\text{mL}

0.150\,\text{M}

Pb(NO

_3

)

_2

is mixed with

100.0\,\text{mL}

0.300\,\text{M}

NaI. Find the mass of PbI

_2

precipitate. (

M_{\text{PbI}_2} = 461.0\,\text{g/mol}

Example 7

medium

A student mixes

20.0\,\text{mL}

0.100\,\text{M}

_2

_3

with

20.0\,\text{mL}

0.100\,\text{M}

CaCl

_2

. Find the mass of CaCO

_3

precipitate. (

M_{\text{CaCO}_3} = 100.1\,\text{g/mol}

Practice Problems

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

Example 1

medium

Will a precipitate form when

\text{Na}_2\text{SO}_4\text{(aq)}

is mixed with

\text{BaCl}_2\text{(aq)}

? Write the equation if a reaction occurs. (Solubility rule:

\text{BaSO}_4

is insoluble.)

Sodium sulfate and barium chloride react; BaSO₄ is the insoluble precipitate

Example 2

hard

A forensic chemist tests a solution suspected of containing

\text{Pb}^{2+}

ions by adding

\text{Na}_2\text{CrO}_4

solution. A yellow precipitate forms. Write the balanced molecular equation, identify the precipitate, and explain how this confirms the presence of lead ions.

Example 3

easy

What is a precipitate?

Example 4

easy

Mixing

AgNO_3

and NaCl gives a white solid. Which product is the precipitate?

Example 5

easy

Will a precipitate form if both products are soluble?

Example 6

easy

Complete:

Pb(NO_3)_2 + 2KI \rightarrow

? (PbI2 is insoluble)

Complete the products: PbI₂ is insoluble

Example 7

easy

Is precipitation a type of which broader reaction class?

Example 8

easy

BaCl_2 + Na_2SO_4 \rightarrow BaSO_4 + 2NaCl

, which is insoluble?

Example 9

easy

How is a precipitate denoted in an equation?

Example 10

easy

Two clear solutions mix and a solid appears. What reaction occurred?

Example 11

medium

Predict and balance:

AgNO_3 + Na_2CO_3 \rightarrow

? (

Ag_2CO_3

insoluble)

Predict and balance: Ag₂CO₃ is insoluble

Example 12

medium

Using solubility rules (nitrates soluble, most sulfates soluble except Ba/Pb/Ca): does

Ba(NO_3)_2 + K_2SO_4

precipitate?

Example 13

medium

Does

NaCl + KNO_3

form a precipitate? Use solubility rules.

Example 14

medium

Predict and balance:

CaCl_2 + Na_2CO_3 \rightarrow

Predict and balance: CaCO₃ is insoluble

Example 15

medium

Identify the spectator ions in

AgNO_3 + NaCl \rightarrow AgCl(s) + NaNO_3

Example 16

medium

Predict and balance:

Pb(NO_3)_2 + K_2CrO_4 \rightarrow

? (

PbCrO_4

insoluble)

Example 17

medium

Why does

AgNO_3 + NaCl

precipitate while

AgNO_3 + NaNO_3

does not?

Example 18

medium

Predict and balance:

FeCl_2 + Na_2S \rightarrow

? (FeS insoluble)

Example 19

medium

Does

KNO_3 + NaCl

form a precipitate? Apply solubility rules.

Example 20

challenge

0.10 mol AgNO3 reacts with excess NaCl. Mass of AgCl (M=143.5) precipitate?

Example 21

challenge

Mixing 0.10 mol

BaCl_2

with 0.15 mol

Na_2SO_4

: mol

BaSO_4

precipitate?

Example 22

challenge

How many mol

Na_2CO_3

are needed to fully precipitate 0.30 mol

CaCl_2

CaCO_3

Example 23

easy

Predict the precipitate when

\text{BaCl}_2\text{(aq)}

is mixed with

\text{K}_2\text{SO}_4\text{(aq)}

Example 24

easy

Write the balanced molecular equation:

\text{CaCl}_2\text{(aq)} + \text{Na}_2\text{CO}_3\text{(aq)} \rightarrow

Example 25

easy

Does mixing

\text{NaCl}\text{(aq)}

and

\text{KNO}_3\text{(aq)}

produce a precipitate?

Example 26

medium

List the spectator ions when

\text{Pb(NO}_3)_2

reacts with

\text{KI}

to give

\text{PbI}_2

Example 27

medium

Write the net ionic equation when

\text{BaCl}_2\text{(aq)}

reacts with

\text{Na}_2\text{SO}_4\text{(aq)}

Example 28

medium

Mixing CuSO

_4

(aq) and NaOH(aq) yields a blue precipitate. Identify it and write the molecular equation.

Example 29

medium

Predict whether mixing

\text{NH}_4\text{Cl}\text{(aq)}

and

\text{KNO}_3\text{(aq)}

produces a precipitate.

Example 30

medium

\text{Fe(NO}_3)_3

is mixed with NaOH, what is the precipitate?

Example 31

hard

Write the complete ionic and net ionic equations for the reaction between aqueous Pb(NO

_3

)

_2

and aqueous Na

_2

_4

Example 32

hard

A solution may contain Ag

^+

, Pb

^{2+}

, or both. Adding HCl gives a white precipitate that dissolves when the mixture is warmed. Identify the metal ion present.

Example 33

hard

Water hardness comes from dissolved Ca

^{2+}

and Mg

^{2+}

. Why does adding Na

_2

_3

soften hard water?

Example 34

medium

What color precipitate confirms the presence of iodide ions when AgNO

_3

is added?

Example 35

hard

Adding dilute NH

_3

(aq) to a solution containing Cu

^{2+}

first gives a blue precipitate, then dissolves to a deep-blue solution on excess NH

_3

. Explain.

Example 36

medium

Why is precipitation considered a type of double-displacement reaction?

Example 37

challenge

25.0\,\text{mL}

0.200\,\text{M}

AgNO

_3

is added to

25.0\,\text{mL}

0.100\,\text{M}

_2

CrO

_4

. Identify the limiting reactant and the mass of Ag

_2

CrO

_4

precipitate. (

M_{\text{Ag}_2}\text{CrO}_4 = 331.7\,\text{g/mol}

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Related Concepts

Double Displacement Solubility Net Ionic Equation

Background Knowledge

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

double displacementsolubility