Physical Chapter 9: Acids & Bases Flashcards

1
Q

What does an acid release?

A

H+ (protons)

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2
Q

What does a base act as?

A

A proton acceptor

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3
Q

What is a characteristic of pure water?

A

[H+] = [OH-]

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4
Q

What is a Bronsted-Lowry base defined as?

A

Any chemical that can accept protons

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5
Q

What is a Bronsted-Lowry acid defined as?

A

Any chemical that releases protons

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6
Q

What happens to a strong acid in water?

A

It fully dissociates.

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7
Q

What happens to a strong base in water?

A

It fully dissociates

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8
Q

What happens to a weak acid/base in water?

A

Partial dissociation - equilbrium position lies well to the left

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9
Q

Does water dissociate on its own?

A

Yes, very slightly

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10
Q

What does water dissociate into?

A

H3O+ & OH-

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11
Q

What is Kw?

A

The ionic product of water - constant

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12
Q

How do you calculate Kw?

A

Kw = [H+][OH-]

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13
Q

What does Kw equal in pure water?

A

Kw = [H+]2

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14
Q

How do you calculate pH?

A

pH = -log10[H+]

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15
Q

How do you calculate hydrogen ion concentration?

A

[H+] = 10-pH

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16
Q

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

A

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

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17
Q

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

A

Kw

18
Q

What is Ka?

A

The dissociation constant

19
Q

How do you calculate Ka for a strong acid?

A

Where HA <-> H+ + A-,

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

20
Q

How do you calculate Ka for a weak acid?

A

Where HA <-> H+ + A-,

Ka = [H+]2/[HA]

21
Q

What are the units for Ka?

A

Moldm-3

22
Q

How do you find pKa from Ka?

A

-log(Ka)

23
Q

How do you find Ka from pKa?

A

10-pKa

24
Q

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

A
25
Q

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

A
26
Q

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

A
27
Q

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

A
28
Q

What are pH curves useful for?

A

Deciding what indicator to use when titrating

29
Q

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

A

Methyl Orange & Phenolphthalein

30
Q

What colour is Methyl orange at low pH?

A

Red

31
Q

What colour is Methyl orange at high pH?

A

Yellow

32
Q

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

A

3-4

33
Q

What colour is Phenolphthalein at low pH?

A

Colourless

34
Q

What colour is Phenolphthalein at high pH?

A

Pink

35
Q

At what pH (roughly) does Phenolphthalein change colour?

A

8-10

36
Q

What is a buffer solution?

A

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

37
Q

What are acidic buffers made of?

A

Weak acid & one of its salts

38
Q

What are basic buffers made of?

A

Weak base & one of its salts

39
Q

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

A

Undissolved acid <-> H+ + salt

e.g. CH3COOH <-> H+ + CH3COO-

40
Q

Why do buffer solutions work?

A

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

41
Q

How can you calculate the pH of a buffer solution?

A

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

42
Q

What are buffer solutions commonly used as?

A

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