Chapter 20 - Acids, Bases, And pH

Question 1

What does the Arrhenius model suggest about acids?

Answer 1

They dissociate and release H+ ions when dissolved in water

Question 2

What does the Arrhenius model suggest about alkalis?

Answer 2

They dissociate and release OH- ions when dissolved in water

Question 3

What is an alkali?

Answer 3

A soluble base

Question 4

What is a Brønsted-Lowry acid?

Answer 4

A proton donor

Question 5

What is a Brønsted-Lowry base?

Answer 5

A proton acceptor

Question 6

What is a conjugate acid-base pair?

Answer 6

Two species that can be interconverted by the transfer of a proton

Question 7

Formula for the hydronium ion

Answer 7

H3O+

Question 8

What does H+ really represent in an equation?

Answer 8

The hydronium ion

Question 9

What type of scale is pH?

Answer 9

Logarithmic

Question 10

What does a low value of H+ indicate?

Answer 10

A high pH

Question 11

What does a high value of H+ indicate?

Answer 11

A low pH

Question 12

How to work out pH?

Answer 12

pH = -log[H+]

Question 13

How to work out [H+]?

Answer 13

10^-pH

Question 14

What is important to remember about calculating the pH of strong acids?

Answer 14

They completely dissociate:

[H+(aq)] = [HA(aq)]

Question 15

What happens to weak acids when dissolved in solution?

Answer 15

They partially dissociate

Question 16

What is Ka?

Answer 16

The acid dissociation constant

Question 17

What does pH measure?

Answer 17

Hydrogen ion concentration

Question 18

What is the equation of Ka for a weak acid before assumptions?

Answer 18

[H+(aq)] x [A-(aq)]

[HA(aq)]

Question 19

How to find pKa?

Answer 19

pKa = -log(Ka)

Question 20

How to find Ka from pKa?

Answer 20

10^-pKa

Question 21

What characteristics of pKa and Ka will a strong acid have?

Answer 21

Large Ka value, small pKa

Question 22

What are spectator ions?

Answer 22

Ions that do not change during reaction

Question 23

General equation for neutralisation of acids with carbonates

Answer 23

Acid + carbonate —> salt + water + carbon dioxide

Question 24

General equation for neutralisation of acid’s with metal oxides

Answer 24

Acid + base —> salt + water

Question 25

General equation for neutralisation of acid’s with alkalis

Answer 25

Acid + alkali —> salt + water

Question 26

What characteristics of pKa and Ka will a weak acid have?

Answer 26

Smaller ka value, lager pka value

Question 27

What are the units for Ka?

Answer 27

Mol dm^-3

Question 28

What is produced when a weak acid dissociates?

Answer 28

HA ->

Question 29

What is the first approximation we use when calculating pH for a weak acid?

Answer 29

Monobasic so [H+]=[A-] On the side there is a very small concentration of H plus ions from the dissociation of water however it is extremely small and will be neglected

Question 30

What is the second approximation we use when calculating pH for a weak acid?

Answer 30

[HA]eqm=[HA]start-[H+]eqm Weak dissociation so [H+] small and neglected so… [HA]eqm=[HA]start

Question 31

What is the simplified version of Ka we get?

Answer 31

Ka = [H+]^2/[HA]

Question 32

How to find [H+] using the simplified Ka expression?

Answer 32

[H+] = (square root) ka X [HA]

Question 33

What experiment would you conduct to measure Ka?

Answer 33

* preparing a standard solution of a weak acid of known concentration * measuring the pH of the standard solution using a pH meter

Question 34

When will approximation 1 break down?

Answer 34

Very weak acids or very dilute solutions

Question 35

When will approximation 2 break down?

Answer 35

Not justified for stronger weak acids with Ka > 10^-2 moldm^-3 and very dilute solutions

Question 36

What is Kw?

Answer 36

The ionic product of water

Question 37

Equation for Kw

Answer 37

Kw = [H+][OH-]

Question 38

What is the value of Kw at RTP?

Answer 38

1X10^-14 mol^2dm^-6

Question 39

Units for Kw

Answer 39

mol^2dm^-6

Question 40

When will a solution be acidic?

Answer 40

[H+]>[OH-]

Question 41

When will a solution be neutral?

Answer 41

[H+]=[OH-]

Question 42

When will a solution be alkaline?

Answer 42

[H+]

Question 43

For a strong base, how do you calculate pH?

Answer 43

[H+] = kw(1X10^-14)/[OH-] | then -log(H+)

Question 44

For a dibasic base, how do you calculate [OH-]?

Answer 44

Each mole of dibasic base releases 2 moles of OH-ions

Question 45

What is monobasic, dibasic, and tribasic acid?

Answer 45

The total number of hydrogen ions in the acid that can be replaced per molecule in an acid-base reaction