Mr Cole Chemistry

Acids and Bases Basics Questions

Acids and Bases Basics

Acids and Bases Worksheet

1. Key Definitions

Define the following terms:
a) Bronsted-Lowry acid

A species that can donate protons (H+ ions).

b) Bronsted-Lowry base

A species that can accept protons (H+ ions).

c) Lewis acid

A species that contains an empty orbital which is capable of accepting an electron pair.

d) Lewis base

A species that can donate a pair of nonbonding electrons.

e) Conjugate acid

A chemical species formed when a base accepts a proton.

f) Conjugate base

A substance formed by the removal of a proton from an acid.

2. Acid Dissociation Equations

Write the following equations.
a) Hydrochloric acid acting as a strong acid in water.
HCl(aq) + H2O(l)
→
H3O+(aq) + Cl–(aq)
b) Ethanoic acid acting as a weak acid in water.
CH3COOH(aq) + H2O(l)
⇌
CH3COO–(aq) + H3O+(aq)
c) Ammonia acting as a weak base in water.
NH3(aq) + H2O(l)
⇌
NH4+(aq) + OH–(aq)

3. Identifying Acid/Base Roles

Identify which reactant is acting as the acid and which as the base in each reaction.
a) HCl + H₂O → H₃O⁺ + Cl⁻

Acid: HCl
Base: H2O
Conjugate Acid: H3O+
Conjugate Base: Cl–

b) NaOH + HCl → NaCl + H₂O

Acid: HCl
Base: NaOH
Conjugate Acid: H2O
Conjugate Base: NaCl (Cl–)

c) HNO₃ + NH₃ → NH₄⁺ + NO₃⁻

Acid: HNO3
Base: NH3
Conjugate Acid: NH4+
Conjugate Base: NO3–

d) CH₃COOH + H₂SO₄ → CH₃COOH₂⁺ + HSO₄⁻

Acid: H2SO4
Base: CH3COOH
Conjugate Acid: CH3COOH2+
Conjugate Base: HSO4–

e) CH₃COOH + CH₃OH → CH₃COO⁻ + CH₃OH₂⁺

Acid: CH3COOH
Base: CH3OH
Conjugate Acid: CH3OH2+
Conjugate Base: CH3COO–

f) HCO₃⁻ + OH⁻ → H₂O + CO₃²⁻

Acid: HCO3–
Base: OH–
Conjugate Acid: H2O
Conjugate Base: CO32-

4. Strength & Trends

State the difference between a strong acid and a weak acid.
Answer

A strong acid fully ionises (dissociates) when dissolved in water. A weak acid only partially ionises.

State which of the following is a stronger acid and explain your answer.
a) Ethanoic acid or chloroethanoic acid?

Chloroethanoic acid is stronger. Due to the negative inductive effect, the chlorine atom withdraws electrons. This results in the COO– ion being less negative (charge is more spread out), making it more stable. Therefore, chloroethanoic acid is more likely to donate the proton and remain ionised.

b) Ethanoic acid or propanoic acid?

Ethanoic acid is stronger. Propanoic acid has a longer alkyl chain which exerts a stronger positive inductive effect. This pushes electron density onto the COO– ion, making it more unstable and more likely to reclaim a proton.

State which of the following is a stronger base and explain your answer.
a) Magnesium oxide or sodium oxide?

Sodium oxide. When dissolved in water, it forms sodium hydroxide (NaOH), which is more soluble than magnesium hydroxide. This results in a higher concentration of OH– ions in solution.

b) Ammonia or methylamine?

Methylamine is stronger. The methyl group exerts a positive inductive effect, pushing electrons towards the nitrogen atom. This makes the lone pair on nitrogen more available to accept a proton.

Use two equations to demonstrate that HSO4– is amphoteric.
Answer

Acting as a Base (Accepting Proton):
HSO4– + H+ ⇌ H2SO4

Acting as an Acid (Donating Proton):
HSO4– ⇌ H+ + SO42-

Note: Because it can act as both an acid and a base, it is termed amphoteric.

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