Acids & Bases

Question 1

Arrhenius definition of an acid

Answer 1

A substance that dissociates in water to produce H+ ions

Question 2

Arrhenius definition: strong acid

Answer 2

A substance that almost completely dissociates in water to give hydrogen ions

Question 3

Arrhenius definition: weak acid

Answer 3

A substance that only slightly dissociates in water to give hydrogen ions

Question 4

Arrhenius definition: Base

Answer 4

A substance that dissociates in water to produce OH- ions

Question 5

Arrhenius definition: Strong base

Answer 5

A substance that almost complexity dissociates in water to give hydroxide ions

Question 6

Arrhenius definition: Weak base

Answer 6

A substance that inky slightly dissociates in water to give hydroxide ions

Question 7

Brønsted-Lowry definition: An acid

Answer 7

A proton donor

Strong acid- good proton donor
Weak acid- poor proton donor

Question 8

Brønsted-Lowry definition: Base

Answer 8

A proton acceptor

Strong base- good proton acceptor
Weak base- poor proton acceptor

Question 9

What are the limitations of the Arrhenius theory?

Answer 9

• Limited to reactions in water (unlike Brønsted-Lowry)
• Limited to bases that produce hydroxide ions in water (not all bases)
• Doesn’t take the existence of hydronium ions into account (unlike BL)

Question 10

Conjugate base

Answer 10

An acid changes into its conjugate base when it donates a proton

Question 11

Conjugate acid

Answer 11

A base changes into its conjugate acid when it accepts a proton

Question 12

Conjugate acid-base pair

Answer 12

Any pair consisting of an acid and a base that differ by one proton

Question 13

A salt

Answer 13

The substance formed when the hydrogen ion from an acid is replaced by a metal or an ammonium ion

Question 14

Neutralisation

Answer 14

The reaction between an acid and a base to form a salt and water

Acid+base—> salt+water

Question 15

Name 3 examples of neutralisation

Answer 15

• MEDICINE, excess HCL produced by stomach—> ulcers, an antacid preparation is taken to neutralise the acid
• AGRICULTURE, if soil is too acidic, farmers spread lime (CaO) to neutralise
• ENVIRONMENTAL PROTECTION, areas that suffer from acid rain, limestone is added to lakes / in tall chimneys of coal burning power plants

Question 16

Amphoteric/ amphiprotic substance

Answer 16

Can act both as an acid and a base

Question 17

Solution

Answer 17

A completely perfect mixture of a solute and a solvent. In a soln. the particles of the solute are uniformly distributed throughout the solvent, I.e. the mixture is homogenous

Question 18

Concentration of a solution

Answer 18

The amount of solute that is dissolved in a given volume of a solution

Question 19

Molarity of a solution

Answer 19

The number of moles of solute per litre of solution

Question 20

A 1M (1 Molar) solution

Answer 20

A solution that contains one mole of the solute dissolved in one litre of solution

Question 21

How do we calculate the number of moles?

Answer 21

Volume x molarity

1000

Question 22

Standard solution

Answer 22

A soln. who’s concentration is accurately known

Question 23

Primary standard

Answer 23

A substance that can be obtained in a stable, pure and soluble solid form so that it can be weighed out and dissolved in water to give a solution of accuracy known concentration

Question 24

Titration

Answer 24

A lab procedures where a measured volume of one solution is added to a known volume of another solution until the reaction is complete

Question 25

Acid rain?

Answer 25

Rain with a pH less than 5.5

Cause: SO2/SO3
Effects: damage to trees, corrosion of limestone buildings

Question 26

Nitrogen fixation?

Answer 26

Converts nitrigen gas—> nitrates