Base Examples in Chemistry

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

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 substance that accepts $\text{H}^+$ ions (protons) or donates $\text{OH}^-$ ions when dissolved in solution, raising the pH above 7.

Slippery substances that can neutralize acids—they remove hydrogen ions.

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: Base starts by identifying the acid/base species, ions produced or transferred, and pH evidence.

Common stuck point: Students often know a formula related to base but skip the recognition step: Am I tracking acid/base identity, pH, ions in solution, neutralization, buffer behavior, or salt formation? That leads to a correct-looking substitution attached to the wrong chemical model.

Sense of Study hint: Ask: Am I tracking acid/base identity, pH, ions in solution, neutralization, buffer behavior, or salt formation?

Common Mistakes to Watch For

Before you work through the examples, skim the mistake guide so you know which shortcuts and sign errors to avoid.

pH Mistakes

Worked Examples

Example 1

easy

According to the Arrhenius definition, what makes a substance a base? Give two examples.

Answer

\text{Bases produce OH}^-\text{ in water: NaOH, KOH}

First step

An Arrhenius base produces

\text{OH}^-

ions (hydroxide) when dissolved in water.

Full solution

2
Example 1: $\text{NaOH} \rightarrow \text{Na}^+ + \text{OH}^-$ (sodium hydroxide).
3
Example 2: $\text{KOH} \rightarrow \text{K}^+ + \text{OH}^-$ (potassium hydroxide).

Bases feel slippery and taste bitter. The Brønsted-Lowry definition broadens this to any proton acceptor, allowing substances like

\text{NH}_3

to be classified as bases.

Example 2

medium

Ammonia (

\text{NH}_3

) is a base but does not contain

\text{OH}^-

. Using the Brønsted-Lowry definition, explain how

\text{NH}_3

acts as a base.

Example 3

medium

Identify whether NaOH is an acid or a base. Write the dissociation equation in water.

Example 4

hard

Why does adding water to a strong base solution change pH by less than the dilution factor near pH 7?

Practice Problems

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

Example 1

easy

Is a solution with pH = 12 acidic, neutral, or basic?

Example 2

easy

A base is added to water. What happens to the hydrogen-ion concentration, and why?

Example 3

easy

By the Arrhenius definition, what ion does a base produce in water?

Example 4

easy

By the Bronsted-Lowry definition, a base is a proton ____.

Example 5

easy

Is the pH of a basic solution above or below 7?

Example 6

easy

Ammonia (

\text{NH}_3

) is a base but has no

\text{OH}^-

in its formula. How can it be a base?

Example 7

easy

Classify

\text{NaOH}

as a strong or weak base.

Example 8

easy

Does 'strong base' refer to degree of dissociation or amount dissolved?

Example 9

easy

Can a base be a solid, like

\text{CaO}

Example 10

easy

Write the ions formed when

\text{NaOH}

dissolves in water.

Example 11

medium

0.01\,\text{M}

NaOH solution has what

[\text{OH}^-]

, pOH, and pH (at 25°C)?

Example 12

medium

Compare

1\,\text{M}

ammonia (weak) and

1\,\text{M}

NaOH (strong). Which has the higher pH and why?

Example 13

medium

Identify the Bronsted-Lowry base in

\text{NH}_3+\text{H}_2\text{O}\rightleftharpoons\text{NH}_4^++\text{OH}^-

Example 14

medium

\text{Ca(OH)}_2

provides how many

\text{OH}^-

per formula unit, and how many moles of

\text{OH}^-

come from

0.5\,\text{mol}

Example 15

medium

0.001\,\text{M}

NaOH solution: find

[\text{OH}^-]

, pOH, and pH.

Example 16

medium

Why can a concentrated weak base have a lower pH than a dilute strong base?

Example 17

medium

Classify each:

\text{KOH}

\text{NH}_3

\text{Mg(OH)}_2

— which is/are bases, and which is a Bronsted base without hydroxide?

Example 18

medium

Identify the conjugate acid of the base

\text{NH}_3

Example 19

medium

0.10\,\text{M}

NaOH solution: find

[\text{OH}^-]

, pOH, and pH at 25°C.

Example 20

challenge

Equal moles of NaOH (strong) and ammonia (weak) are each dissolved to the same volume. Which neutralizes more HCl, and why?

Example 21

challenge

0.01\,\text{M}

NaOH solution is diluted tenfold. Find the new pH (ignore water autoionization).

Example 22

challenge

\text{Ba(OH)}_2

is a strong base. For a

0.005\,\text{M}

solution, find

[\text{OH}^-]

and pH.

Example 23

easy

Is a solution with pH 9 acidic, neutral, or basic?

Example 24

easy

Name a common household base.

Example 25

easy

Write the dissociation of KOH in water.

Example 26

easy

\text{Mg(OH)}_2

a base?

Example 27

easy

Which is a stronger base: NaOH or

\text{NH}_3

Example 28

easy

Does litmus paper turn red or blue in a basic solution?

Example 29

medium

Calculate the pH of a 0.025 M KOH solution at 25°C.

Example 30

medium

Write the dissociation of

\text{Ca(OH)}_2

in water.

Example 31

medium

Identify the conjugate base of

\text{HCO}_3^-

acting as an acid.

Example 32

medium

\text{NH}_3 + \text{H}_2\text{O} \rightleftharpoons \text{NH}_4^+ + \text{OH}^-

. Identify both Bronsted bases in this equilibrium.

Example 33

medium

What is

[\text{H}^+]

in a solution with pH = 12 at 25°C?

Example 34

medium

Why does

\text{NH}_3

act as a base in water without donating

\text{OH}^-

Example 35

medium

Predict the pH of a 0.0010 M KOH solution at 25°C.

Example 36

medium

Compare 0.05 M

\text{Ba(OH)}_2

with 0.10 M NaOH. Which has the higher pH?

Example 37

hard

Compute the pH of a solution made by dissolving 4.0 g NaOH (

M=40

) in 500 mL water.

Example 38

hard

Find the pH of a 0.05 M

\text{Ba(OH)}_2

solution at 25°C.

Example 39

hard

100 mL of 0.10 M NaOH is diluted to 1.0 L. What is the new pH at 25°C?

Example 40

hard

Identify the conjugate acid-base pairs in

\text{HCl} + \text{NH}_3 \rightarrow \text{NH}_4^+ + \text{Cl}^-

Example 41

hard

If 25.0 mL of 0.20 M HCl is added to 25.0 mL of 0.20 M NaOH, what is the resulting pH (assume 25°C)?

Example 42

challenge

A 0.20 M aqueous solution of methylamine has pH = 11.85. Estimate the

K_b

of methylamine.

Example 43

challenge

Equal volumes of 0.10 M NaOH and 0.10 M

\text{NH}_3

are mixed. Which has higher resulting pH and why?

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Related Concepts

Ion Acid pH Neutralization

Background Knowledge

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

ion