acids and bases

Question 1

Define acids according to Arrhenius theory.

Answer 1

Substances that produce hydrogen ions (H+/H3O+/hydronium ions) in aqueous solution.

Question 2

Define bases according to Arrhenius theory.

Answer 2

Substances that produce hydroxide ions (OH-) in aqueous solution.
Substances that react with H+(aq) to form a salt and water, with or without other products

Question 3

What does the extension of the Arrhenius definition of a base result in?

Answer 3

Neutralisation reactions in aqueous medium to form salt and water

Question 4

Limits of Arrhenius model

Answer 4

1. Limits acids to substances soluble in water
2. Limits acid-base reactions to aqueous solutions

Question 5

Define a proton

Answer 5

The positive ion H+ derived from a H- atom by the removal of its electron

Question 6

Define acids according to Lowry-Brønsted theory.

Answer 6

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

Question 7

Define bases according to Lowry-Brønsted theory.

Answer 7

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

Question 8

Therefore, what happens in an acid-base reaction according to L-B model?

Answer 8

Proton(s) transferred from acid to base

Question 9

What is the reaction as a result of L-B theory in practice and give definition for it

Answer 9

Protolysis is a reaction in which proton transfer takes place
L-B a-b reactions are protolytic

Question 10

Define a conjugate acid-base pair

Answer 10

A reactant and a product that can be obtained from one another by the addition or removal of one proton (H+).

Question 11

Define a conjugate acid

Answer 11

A conjugate acid in a conjugate acid-base pair is obtained from the base by addition of one proton (H+)

Question 12

Define a conjugate base

Answer 12

A conjugate base in a conjugate acid-base pair is obtained from an acid by removal of one proton (H+)

Question 13

What is a strong acid?

Answer 13

Acids that ionise completely in water to form a high concentration of H3O+ ions.

Question 14

Examples of strong acids.

Answer 14

Hydrochloric acid, sulphuric acid, nitric acid (NHS)

Question 15

What is a weak acid?

Answer 15

Acids that ionise incompletely in water to form a low concentration of H3O+ ions.

Question 16

Examples of weak acids.

Answer 16

Ethanoic acid and oxalic acid

Question 17

What is a strong base?

Answer 17

Bases that dissociate completely in water to form a high concentration of OH- ions.

Question 18

Examples of strong bases

Answer 18

Sodium hydroxide and potassium hydroxide

Question 19

What are weak bases?

Answer 19

Bases that dissociate incompletely in water to form a low concentration of OH- ions.

Question 20

Examples of weak bases

Answer 20

Ammonia, calcium carbonate, potassium carbonate, calcium carbonate and sodium hydrogen carbonate

Question 21

What is another distinction of acids and bases?

Answer 21

Concentrated and dilute

Question 22

What is a concentrated acid/base?

Answer 22

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

Question 23

What is a dilute acid/base?

Answer 23

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

Question 24

Define ampholyte

Answer 24

A substance that can act as acid and base

Question 25

Substances that are ampholytes are … or … substances

Answer 25

Amphiprotic Amphoteric

Question 26

Examples of a ampholytes

Answer 26

Water NH3 HSO4- HCO3-

Question 27

Define proticity

Answer 27

The proticity of an acid is the number of protons that it can donate per formula unit

Question 28

Types of proticity

Answer 28

A monoprotic acid can donate “one” proton Diprotic “two” Triprotic “three”

Question 29

Acids that can donate more than one proton per formula unit

Answer 29

Polyprotic acids

Question 30

Define hydrolysis.

Answer 30

A reaction between a salt and water (formed from neutralisation) to form a solution that is acidic or basic

Question 31

What determines pH of solution of hydrolysis?

Answer 31

Relative strengths of acids and bases creating salt

Question 32

Hydrolysis of salt of weak acid and strong base produces

Answer 32

Alkaline (basic) solution where pH > 7

Question 33

Examples of salts from weak acid and strong base

Answer 33

Sodium ethanoate, sodium oxalate, sodium carbonate

Question 34

Hydrolysis of salt of strong acid and weak base

Answer 34

Acidic solution (pH < 7)

Question 35

Example of salt from strong acid and weak base

Answer 35

Ammonium chloride

Question 36

Salt of strong acid and strong base

Answer 36

Not undergo hydrolysis Solution neutral (pH = 7)

Question 37

What reaction occurs as a result of amphoteric substances

Answer 37

Auto-ionisation / autoprotolysis / self-protolysis

Question 38

What is autoionisation?

Answer 38

Amphoteric substances donate protons that are accepted by another molecule of the same substance in the same liquid

Question 39

How do you write autoprotolysis in an equation?

Answer 39

Substance + substance > products Or work from half reactions first to get net reaction

Question 40

What is a common occurrence of self-protolysis?

Answer 40

Water

Question 41

Chemical equilibrium (understanding not definition)

Answer 41

Net change of solution is 0 as forward and reverse reactions occurring at same rate

Question 42

When water autoionisation is at chemical equilibrium, we get

Answer 42

Pure water

Question 43

When an equation is at equilibrium

Answer 43

Double arrow

Question 44

Homogeneous reaction (understanding not learn)

Answer 44

States of matter of products and reactions same

Question 45

Heterogeneous reaction (understanding not learn)

Answer 45

One or more states within reaction differ

Question 46

Why is it important to understand the difference between homo and hetero exns?

Answer 46

Treated differently when calculating equilibrium constants - remember they deal with the “state” - HA - of the products and reactants when they are unchanging so we have to see what they’re like ykyk to see whats happening on a microscopic scale amirgiht or amiright

Question 47

So, what is an equilibrium constant?

Answer 47

Relationship between products and reactants of a reaction at equilibrium with respect to a specific unit (concentration or pressure) - i.e. how much of this and how much of that so that the forward and reverse rates of reaction are equal

Question 48

Therefore, what does the equilibrium constant consist of?

Answer 48

RATIO between units of products and reactants Therefore it is a fraction

Question 49

Kw also known as…

Answer 49

Ionic product Autoprotolytic constant Dissociation constant Of water

Question 49

Kw

Answer 49

[H3O+][OH-]

Question 50

What is the concentration of H3O+ and OH- in pure water (neutral)?

Answer 50

10-7

Question 51

Therefore… Kw =

Answer 51

10-14

Question 52

What is Kw used for?

Answer 52

CONSTANT value as baseline of all solutions at 25C regardless of acidity to see if more hydronium or hydroxide from acidity/alkalinity

Question 53

Solution neutral if

Answer 53

[H3O+] = [OH-] = 10-7

Question 54

Solution acidic if

Answer 54

[H3O+] > 10-7

Question 55

Solution basic if

Answer 55

[H3O+] < 10-7

Question 56

pH scale

Answer 56

1-6 : acid 7 : neutral 8-14 : base

Question 57

Where does pH scale come from?

Answer 57

Exponent of concentration of H3O+

Question 58

Therefore, what do we use to get pH?

Answer 58

Logs to isolate the exponent

Question 59

how to think of log laws

Answer 59

As exponents and their laws

Question 60

What is calculation to get pH

Answer 60

Log 1/[H3O+] Bc exponent and put in denominator so negative exponent canceled when brought to top -log [H3O+] Other way to cancel negative