Topic 8: Acids and Bases

Question 1

What is calcination?

Answer 1

A process that refers to the heating of materials to very high temperatures in air in order to bring about their thermal decomposition (in the case of limestone), the removal of water from a hydrated compound (for bauxite), or the removal of a volatile matter from minerals and ores.

Question 2

Define neutralisation reaction.

Answer 2

A combination of an acid and base, ie. reaction involving H^(+) and OH^(-)

Question 3

Define an acid

Answer 3

A proton donor.

Question 4

Define a base.

Answer 4

A proton acceptor.

Question 5

How is hydronium ion formed?

Answer 5

Hydronium ion, H3O^(+) is formed when a water molecule form a coordinate bond with a proton.

Question 6

What is a conjugate acid-base pair?

Answer 6

When a conjugate acid and base differ from one another by a single proton.

Question 7

What are amphiprotic species?

Answer 7

Substances that have the ability to act as either Bronsted-Lowry acid or Bronstead-Lowry base depending on the reaction in which they are taking part.

Question 8

What colour is litmus for acid?

Answer 8

red

Question 9

What colour is litmus for base?

Answer 9

blue

Question 10

What colour is phenolphthalein for acid?

Answer 10

colourless

Question 11

What colour is phenolphthalein for base?

Answer 11

pink

Question 12

What colour is methyl orange for acid?

Answer 12

red

Question 13

What colour is methyl orange for base?

Answer 13

yellow

Question 14

acid + metal

Answer 14

salt + hydrogen

Question 15

Define salt.

Answer 15

Compound composed of an anion and cation

Question 16

Define standard enthalpy change of neutralisation

Answer 16

The energy change associated with the formation of 1 mol of water from the reaction between a strong acid and a strong base under standard conditions.
Has a negative value, because neutralisation is an exothermic process.

Question 17

acid + base

Answer 17

salt + water

Question 18

List common bases

Answer 18

metal hydroxides
metal oxides
ammonium hydroxide

Question 19

Define an alkali

Answer 19

A soluble base.

Question 20

acid + metal carbonate/metal hydrogencarbonate

Answer 20

salt + carbon dioxide + water

Question 21

What is titration?

Answer 21

A volumetric analysis technique that involves a reaction between a substance of unknown concentration with a standardized solution (the titrant)

Question 22

What is a pH scale?

Answer 22

represents the concetration of hydrogen ions, [H^(+)] in a solution.

Question 23

List two expressions that define the pH of a solution.

Answer 23

1) pH = -log[H^(+)(aq)]

or

pH = -log[H3O^(+)(aq)]

2) [H^(+)] = 10^(-pH)

Question 24

What is the ion product constant of water, Kw?

Answer 24

Kw = [H^(+)][OH^(-)] = 1.0 x 10^(-14) at 298K

Question 25

ionization

Answer 25

dissociation

Question 26

List three examples of strong acids

Answer 26

HCl H2SO4, Sulfuric acid HNO3, nitric acid

Question 27

Define amphoteric

Answer 27

species that behaves both as an acid and a base, eg. aluminum hydroxide

Question 28

Describe the enthalpy changes in a neutralisation reaction involving strong acid or base.

Answer 28

A strong acid or base completely dissociates in a solution, so the only enthalpy consideration is the exothermic formation of water from hydrogen and hydroxide ions.

Question 29

Describe the enthalpy changes in a neutralisation reaction involving weak acid or base.

Answer 29

Weak acid or base is predominantly in their undissociated form in aqueous solution. The ionisation is mildly endothermic. Thus the neutralisation will be less exothermic than for strong acid or base.

Question 30

Define acid deposition

Answer 30

Process by which acid-forming pollutants are deposited on the Earth's surface. It affects the environment by e.g. deforestation, leaching of minerals from soils leading to elevated acid levels in lakes and rivers, etc

Question 31

What is acid rain?

Answer 31

Form of acid deposition caused by increased emissions of nitrogen and sulfur oxides. the pH of rainwater is 5.6 due to CO2 that forms the weak carbonic acid, however acid rain is <5.6 is the results of the formation of two strong acids: nitric acid (HNO3) and sulfuric acid (H2SO4)