Physical Chapter 9: Acids & Bases

Question 1

What does an acid release?

Answer 1

H⁺ (protons)

Question 2

What does a base act as?

Answer 2

A proton acceptor

Question 3

What is a characteristic of pure water?

Answer 3

[H⁺] = [OH^-]

Question 4

What is a Bronsted-Lowry base defined as?

Answer 4

Any chemical that can accept protons

Question 5

What is a Bronsted-Lowry acid defined as?

Answer 5

Any chemical that releases protons

Question 6

What happens to a strong acid in water?

Answer 6

It fully dissociates.

Question 7

What happens to a strong base in water?

Answer 7

It fully dissociates

Question 8

What happens to a weak acid/base in water?

Answer 8

Partial dissociation - equilbrium position lies well to the left

Question 9

Does water dissociate on its own?

Answer 9

Yes, very slightly

Question 10

What does water dissociate into?

Answer 10

H₃O⁺ & OH^-

Question 11

What is Kw?

Answer 11

The ionic product of water - constant

Question 12

How do you calculate Kw?

Answer 12

Kw = [H+][OH-]

Question 13

What does Kw equal in pure water?

Answer 13

Kw = [H+]²

Question 14

How do you calculate pH?

Answer 14

pH = -log₁₀[H⁺]

Question 15

How do you calculate hydrogen ion concentration?

Answer 15

[H⁺] = 10^-pH

Question 16

What is the difference in [H+] for monoprotic & diprotic aicds?

Answer 16

Monoprotic = conc. H+ equals conc. acid
Diprotic = conc. H+ equals 2x conc. acid

Question 17

What constant do you use to find the pH of a strong base?

Answer 17

Kw

Question 18

What is Ka?

Answer 18

The dissociation constant

Question 19

How do you calculate Ka for a strong acid?

Answer 19

Where HA <-> H⁺ + A^-,

K_a = [H+][A-]/[HA]

Question 20

How do you calculate Ka for a weak acid?

Answer 20

Where HA <-> H⁺ + A^-,

K_a = [H+]²/[HA]

Question 21

What are the units for Ka?

Answer 21

Moldm^-3

Question 22

How do you find pKa from Ka?

Answer 22

-log(Ka)

Question 23

How do you find Ka from pKa?

Answer 23

10^-pKa

Question 24

What does the pH curve for a combo of a strong acid with a strong base look like?

Answer 24

Question 25

What does the pH curve for a combo of a strong acid with a weak base look like?

Answer 25

Question 26

What does the pH curve for a combo of a weak acid with a strong base look like?

Answer 26

Question 27

What does the pH curve for a combo of a weak acid with a weak base look like?

Answer 27

Question 28

What are pH curves useful for?

Answer 28

Deciding what indicator to use when titrating

Question 29

What are two commonly used indicators that aren't UI?

Answer 29

Methyl Orange & Phenolphthalein

Question 30

What colour is Methyl orange at low pH?

Answer 30

Red

Question 31

What colour is Methyl orange at high pH?

Answer 31

Yellow

Question 32

At what pH (roughly) does Methyl orange change colour?

Answer 32

3-4

Question 33

What colour is Phenolphthalein at low pH?

Answer 33

Colourless

Question 34

What colour is Phenolphthalein at high pH?

Answer 34

Pink

Question 35

At what pH (roughly) does Phenolphthalein change colour?

Answer 35

8-10

Question 36

What is a buffer solution?

Answer 36

A solution that resists change in pH when small amounts of acid or base are added, or when it's diluted.

Question 37

What are acidic buffers made of?

Answer 37

Weak acid & one of its salts

Question 38

What are basic buffers made of?

Answer 38

Weak base & one of its salts

Question 39

What is the general formula for the equilibrium of a buffer?

Answer 39

Undissolved acid <-> H⁺ + salt e.g. CH₃COOH <-> H⁺ + CH₃COO^-

Question 40

Why do buffer solutions work?

Answer 40

The position of equilbrium will shift to counteract the change you impose on it, and therefore pH will be maintained.

Question 41

How can you calculate the pH of a buffer solution?

Answer 41

use the Ka of the weak acid to calculate [H⁺]

Question 42

What are buffer solutions commonly used as?

Answer 42

Contained in shampoos Biological washing powders Biological buffer solutions in the blood