Acids

Question 1

What is an acid?

Answer 1

A proton H+ donor- a substance that realises hydrogen ions in aqueous solution.

Question 2

What is a base?

Answer 2

A proton H+ acceptor- a substance that reacts with an acid to neutralise it and form a salt and water.

Question 3

What is an alkali?

Answer 3

A soluble base that releases OH- ions in aqueous solution.

Question 4

What is a strong acid?

Answer 4

An acid that completely dissociates into ions in aqueous solution

Question 5

What is a weak acid?

Answer 5

An. Acid that only partially dissociates into ions aqueous solution.

Question 6

What is meant by a monophonic acid?

Answer 6

An acid that donates one proton per molecule eg. HCL

Question 7

What is meant by a diprotic acid?

Answer 7

An acid that donates two protons per molecule eg. H2SO4

Question 8

What is a conjugate acid-base pair?

Answer 8

Two species that differ by one proton.

Question 9

Write the general equation for acid-metal reaction.

Answer 9

Acid + metal - salt + hydrogen

Question 10

Write the general equation for acid-base reaction.

Answer 10

Acid + Base — salt + water

Question 11

Write the general equation for acid- carbonate reaction.

Answer 11

Acid + carbonate — salt + water + carbon dioxide

Question 12

What is a salt?

Answer 12

A compound formed when the hydrogen ions in an acid is replaced by a metal ion or ammonium ion.

Question 13

Ionic equation for neutralisation.

Answer 13

H plus + OH minus — water

Question 14

What is a titration?

Answer 14

An analytical technique used to determine the exact concentration of a solution by reacting it with another of known concentration.

Question 15

Name common indicators and their colour changes in titrations.

Answer 15

Phenolphthalein: colourless — pink
Methyl orange: yellow

Question 16

Define a Bronsted–Lowry acid and base.

Answer 16

Acid: A proton (H⁺) donor.
Base: A proton (H⁺) acceptor.

Question 17

What is a strong acid?

Answer 17

An acid that completely dissociates in aqueous solution to release all its hydrogen ions.

Question 18

What is a weak acid?

Answer 18

An acid that only partially dissociates in aqueous solution, establishing an equilibrium between the undissociated acid and its ions.

Question 19

What is a monoprotic acid? Give one example.

Answer 19

An acid that can donate one proton per molecule, e.g. HCl.

Question 20

What is a diprotic acid? Give one example.

Answer 20

An acid that can donate two protons per molecule, e.g. H₂SO₄.

Question 21

Write the equation for the neutralisation of HCl with NaOH.

Answer 21

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Question 22

Write the ionic equation for any acid–base neutralisation.

Answer 22

H⁺(aq) + OH⁻(aq) → H₂O(l)

Question 23

Define a neutralisation reaction.

Answer 23

A reaction between an acid and a base to form a salt and water.

Question 24

How does an acid–metal reaction proceed? Give the general equation.

Answer 24

Acid + Metal → Salt + Hydrogen
e.g. 2HCl(aq) + Mg(s) → MgCl₂(aq) + H₂(g)

Question 25

How does an acid–carbonate reaction proceed?

Answer 25

Acid + Carbonate → Salt + Water + Carbon dioxide
e.g. 2HCl(aq) + CaCO₃(s) → CaCl₂(aq) + H₂O(l) + CO₂(g)

Question 26

What is a salt?

Answer 26

A compound formed when the hydrogen ion of an acid is replaced by a metal ion or ammonium ion (NH₄⁺).

Question 27

What is the difference between a base and an alkali?

Answer 27

A base neutralises an acid.
An alkali is a soluble base that releases OH⁻ ions in aqueous solution.

Question 28

How do you calculate moles of H⁺ ions in a solution of a diprotic acid?

Answer 28

Moles of H⁺ = (number of H⁺ ions per molecule) × (moles of acid).

Question 29

What apparatus and steps are used in an acid–base titration (outline only)?

Answer 29

* Use a burette for the solution of known concentration. * Use a pipette to measure the other solution. * Add a few drops of indicator to the conical flask. * Add titrant until colour change (endpoint). * Repeat for concordant titres (±0.10 cm³).


Question 30

What are suitable indicators for strong acid–strong base titrations?

Answer 30

* Methyl orange or phenolphthalein. * Choose indicator whose colour change range matches the vertical part of pH curve.

Question 31

Write the formula for the ethanoate ion and name its conjugate acid.

Answer 31

Ethanoate ion: CH₃COO⁻
Conjugate acid: Ethanoic acid (CH₃COOH).

Question 32

What is a conjugate acid–base pair?

Answer 32

Two species that differ by a single proton (H⁺).

Question 33

Describe what happens in an acid–base conjugate pair equilibrium.

Answer 33

The acid donates a proton to form its conjugate base; the base accepts a proton to form its conjugate acid.