CHEMICAL CHANGE: ACIDS AND BASES

Question 1

Acid-base indicator

Answer 1

A substance that can act as either an acid or a base.

Question 2

Arrhenius theory

Answer 2

An acid is a substance that produces hydrogen ions (H+)/ hydronium ions (H3O+) when it dissolves in water. A base is a substance that produces hydroxide ions (OH-) when it dissolves in water.

Question 3

Amphiprotic substance/ampholyte

Answer 3

A substance that can act as either an acid or a base.

Question 4

Auto-ionisation of water

Answer 4

A reaction in which water reacts with itself to form ions (hydronium ions and hydroxide ions).

Question 5

Concentrated acids/bases

Answer 5

Contain a large amount (number of moles) of acid/base in proportion to the volume of water.

Question 6

Conjugate acid-base pair

Answer 6

A pair of compounds or ions that differ by the presence of one H+ ion.

Question 7

Conjugate acid and base

Answer 7

A conjugate acid has one H+ ion more than its conjugate base.

Question 8

Dilute acids/bases

Answer 8

Contain a small amount (number of moles) of acid/base in proportion to the volume of water.

Question 9

Diprotic acid

Answer 9

An acid that can donate two protons. Example: H2SO4

Question 10

Dissociation

Answer 10

The process in which ionic compounds split into ions.

Question 11

Endpoint

Answer 11

The point in a titration where the indicator changes colour.

Question 12

Equivalence point

Answer 12

The point in a reaction where equivalent amounts of acid and base have reacted completely.

Question 13

Hydrolysis

Answer 13

The reaction of a salt with water. OR The reaction of an ion with water to produce the conjugate acid and a hydroxide ion or the conjugate base and a hydronium ion.

Question 14

Ionisation

Answer 14

The process in which ions are formed during a chemical reaction.

Question 15

Ion product of water

Answer 15

The product of the ions formed during auto-ionisation of water i.e. [H3O+][OH–] at 25 °C.

Question 16

Ionisation constant of water (Kw)

Answer 16

The equilibrium value of the ion product [H3O+][OH–] at 25 °C.

Question 17

Ka value

Answer 17

Ionisation constant for an acid.

Question 18

Kb value

Answer 18

Dissociation or ionisation constant for a base.

Question 19

Lowry-Brønsted theory

Answer 19

An acid is a proton (H+ ion) donor.
A base is a proton (H+ ion) acceptor.

Question 20

Monoprotic acid

Answer 20

An acid that can donate one proton. Example: HCℓ

Question 21

Neutralisation

Answer 21

The reaction of an acid with a base to form a salt (ionic compound) and water.

Question 22

pH

Answer 22

The negative of the logarithm of the hydronium ion concentration in mol·dm-3.
In symbols: pH = -log[H3O+]
Unit: None

Question 23

pH scale

Answer 23

A scale from 0 – 14 used as a measure of the acidity and basicity of solutions where
pH = 7 is neutral,
pH > 7 is basic and
pH < 7 is acidic.

Question 24

Salt

Answer 24

The ionic compound that is the product of a neutralisation reaction.

Question 25

Standard Solution

Answer 25

A solution of precisely known concentration.

Question 26

Strong bases

Answer 26

Dissociate COMPLETELY in water to form a high concentration of OH- ions. Examples: sodium hydroxide (NaOH) and potassium hydroxide (KOH)

Question 27

Strong acids

Answer 27

Ionise completely in water to form a high concentration of H3O+ ions. Examples: hydrochloric acid (HCℓ), sulphuric acid (H2SO4) and nitric acid (HNO3)

Question 28

Titration

Answer 28

The procedure for determining the amount of acid (or base) in a solution by determining the volume of base (or acid) of known concentration that will completely react with it.

Question 29

Weak acids

Answer 29

Ionise INCOMPLETELY in water to form a low concentration of H3O+ ions. Examples: ethanoic acid (CH3COOH) and oxalic acid (COOH)2

Question 30

Weak bases

Answer 30

Dissociate/ionise incompletely in water to form a low concentration of OH- ions. Examples: ammonia (NH3), sodium hydrogen carbonate (NaHCO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), calcium carbonate (CaCO3)