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MPW chemistry > Acids, Bases and Buffers > Flashcards

Acids, Bases and Buffers Flashcards

1
Q

what is a salt?

A

A compound formed when the hydrogen ion from an acid is replaced by a metal ion or ammonium ion

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2
Q

what is an alkali?

A

A soluble base which dissolves in water to release OH- ions

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3
Q

what do acids release in water?

A

H+ ions

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4
Q

what do alkalis release in water?

A

OH- ions

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5
Q

What is a Brønsted–Lowry acid

A

proton (H+ ion) donator

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6
Q

What is a Brønsted–Lowry base

A

proton (H+ ion) acceptor

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7
Q

What is a conjucate acid/base pair?

A

Pair of species which differ by the loss or gain of an electron

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8
Q

what is Kw?

A

The ionic product of water

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9
Q

what is the equation for Kw?

A

Kw = [H+][OH-]

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10
Q

What is the numerical value of Kw?

A

1.00 x 10-14 mol2 dm-6

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11
Q

As temperature increases, what happens to kw?

A

kw increases

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12
Q

what is the relationship of [OH-], [H+] and Kw in a neutral solution

A

[OH-] = [H+]

Kw = [H+]2

[H+] = √Kw

=√1 x 10-14

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13
Q

what is the simple pH equation?

A

pH = -log [H+]

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14
Q

what is the simple [H+] equation?

A

[H+] = 10-pH

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15
Q

what is the simple equation for pOH?

A

pH = -log [OH-]

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16
Q

What is the simple equation for [OH-]?

A

[OH-] = 10-pOH

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17
Q

what is a strong acid?

A

An acid which completely dissociates in water to form H+ ions.

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18
Q

what is a weak acid?

A

An acid which partially dissociates in water to form H+ ions.

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19
Q

what is a strong base?

A

A base which completely dissociates in water to form OH- ions.

20
Q

what is a weak base?

A

A base which partially dissociates in water to form OH- ions.

21
Q

Define the Acid dissociation constant

A
22
Q

what is the Ka like in weak acids?

A

Fewer ion ∴ smaller Ka

23
Q

what is the Ka like in strong acids?

A

more ion ∴ larger Ka

24
Q

what does Ka measure?

A

The extent of ionisation

25
Q

how do you calculate pka from Ka?

A

-log(Ka)

26
Q

How do you calculate Ka from pKa?

A

10-pKa

27
Q

what is the Ka and pKa like in strong acids?

A

high Ka

low pKa

28
Q

what is the Ka and pKa like in weak acids?

A

low Ka

high pKa

29
Q

what do we use to compare the strengths of weak acids?

A

Ka

30
Q

how to work out pH of strong acids

A

conc of acid = [H+]

pH = -log [H+]

31
Q

how to work out conc of strong acids

A

[H+] = 10-pH

[H+] = Conc of acid

32
Q

how to work out pH of stong bases

A

Kw = [H+][OH-]

[H+] = Kw/[OH-]

Kw = 1.00 x 10-14

[H+] = 1.00 x 10-14/[OH-]

pH = -log [H+]

33
Q

how to work out conc of strong base

A

[H+] = 10-pH

Kw = [H+][OH-]

[OH-] = Kw/[H+]

Kw = 1.00 x 10-14

[OH-] = 1.00 x 10-14/[H+]

34
Q

How to calculate pH of weak acid

A

Ka = [H+]2 / [HA]

[H+]2 = Ka x [HA]

[H+] = √Ka x [HA]

35
Q

How to calculate conc of weak acid

A

[H+] = 10-pH

Ka = [H+]2/[HA]

36
Q

Ka and pKa circle

A
37
Q

[H+] and pH circle

A
38
Q

what is a buffer solution?

A

a solution which minimises changes in pH when small amounts of acid or base are added

39
Q

what is the order of words you need to know about buffers when pH falls?

A
  1. [H+] rises

(H+ + A- —> HA)

[H+] decreases

equilibrium moves to the acid to decrease [H+]

40
Q

what is the order of words you need to know about buffers when pH rises?

A

[OH-] increases

Neutralisation of OH- (H+ + OH- —–> H2O)

the equilibrium move to the products to increase [H+]

Acid dissociates to oppose [H+] decrease

41
Q

what is buffer equation?

A
42
Q
A
43
Q
A
44
Q
A
45
Q

What are the approximations in calculating weak acids?

A
  1. The dissociation of water is negligible (Doesnt work for very weak acids)

[H+] ~ [A-]

  1. the conc of acid is much greater than the conc of H+

(this works for weak acids with a low Ka, but as strenth increases this doesnt work)

46
Q
A

MPW chemistry (14 decks)

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