Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > acids and bases > Flashcards

acids and bases Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What is an acid base equilibira?

A

In this essay I will argue
that, although mental states are physical things, they are not identical to brain states and thus
type identity theory is incorrect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define a Bronsted Lowry acid

A

A proton donor

Eg NH4+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define a Bronsted Lowry base

A

A proton acceptor

Eg OH-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define concentration

A

how many moles are in a given volume of solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define acid strength

A

The strength is a measure of how ionised the acid is in solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What’s the difference between a strong acid and a weak acid?

A

A strong acid will fully ionise in solution whereas a weak acid will partially ionise in solution.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is pH

A

a measure of the concentration of hydrogen ions in solution.

As the concentration of hydrogen ions for a strong acid is very high, yet the concentration of hydrogen ions for a strong alkali is very low a logarithmic scale must be used.
So,
pH = -log10[H+].

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

equation to determine [H+] with ph

A

[H+] = 10^–pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Write an equation for the dissossiation of sulfuric acid in water

A

H2SO4(l) → 2H+(aq) + SO42–(aq)

Diprotic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What causes a solution to be acidic?

A

H+ (hydrogen ion), or more accurately H3O+ (hydroxonium ion), protons react with H2O to form it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain the dissociation of water

A

Water very slightly dissociates into its ions according to the following equation:
2H2O(l) ⇋ H3O+(aq) + OH-(aq)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Write an equation for the ionisation of water

A

2H2O ⇌ H3O+ + OH
//
H2O ⇌ H++ OH-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Explain the nature of the formation of hydroxonium and OH- ions

A

hydroxonium ion is a very strong acid, and the hydroxide ion is a very strong base. As fast as they are formed, they react to produce water again.

The net effect is that an equilibrium is set up.

2H2O(l) ⇋ H3O+(aq) + OH-(aq)

At any one time, there are incredibly small numbers of hydroxonium ions and hydroxide ions present. (The H2O is in large excess)

Water very slightly dissociates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Derive Kw using the equation for the ionisation of water

A

H2O ⇌ H++ OH-
Keq = [H+] [OH-]/ [H2O]
Keq [H2O] = [H+][OH-]
[H2O] is so large compared to [H+] and [OH-] that Keq[H2O] can be considered to be constant
Keq[H2O] = Kw
Therefore, Kw = [H+][OH-]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the difference between ionising and dissassociating?

Just an NB

A

Ionisation is the process that involves the formation of ions whereas dissociation is the process of breaking up of a moiety into its constituent atoms, molecules and ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What ius the value of Kw at room temperature (25 *C)

A

1 x 10 ^-14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the forward reaction of the ionisation of water

A

endothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Is the forward or backward reaction favoured when temperature of water is increased?

A

Forward, because its endothermic.. so more [H+] is produced so becomes more acidic, pH decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What physical factors affect the value of Kw? How do they affect it?

A

Temperature only- if temperature is increased, the equibilibium moves to the right so Kw increases and the pH of opure water decreases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why is pure water still neutral, even if pH does not equal 7?

A

[H+]=[OH-]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the realtionship between pH and conc of H+?

A

Lower pH= higher concentration of H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

If two solutiuons have a pH difference of 1, what is the difference in [H+]?

A

A factor of 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Why does pure water have a pH of 7?

A

That question is actually misleading! In fact, pure water only has a pH of 7 at a particular temperature - the temperature at which the Kw value is 1.00 x 10-14 mol2 dm-6.

In pure water at room temperature the Kw value tells you that:
[H+] [OH-] = 1.00 x 10-14

But in pure water, the hydrogen ion (hydroxonium ion) concentration must be equal to the hydroxide ion concentration. For every hydrogen ion formed, there is a hydroxide ion formed as well.

That means that you can replace the [OH-] term in the Kw expression by another [H+].

[H+]2 = 1.00 x 10-14

Taking the square root of each side gives:

[H+] = 1.00 x 10-7 mol dm-3

Converting that into pH:

pH = - log10 [H+]

pH = 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How would you calculate pH of 0.0500 mol dm-3 Ba(OH)2

A

[OH-]= 0.05 x 2
[H+] = kw/ [OH-]
[H+] = 10^-14/ 0.1
pH = -log [H+]
pH= -log [1.00 x 10^-13]
pH = 13.00

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How would you calculate [H+] of [Ba(OH)2] with pH 13.30?

A

[H+] = 10 ^-pH
[H+] = 10 ^-13.3 = 5.01x10^-14
[OH-] = Kw/[H+]
[OH-]=10^-14/ 5.01x10^-14 = 0.2
[Ba(OH)2] = 0.2 x 1/2 = 0.100 mold dm^-3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Give examples of strong monoprotic acids

A

HCl, HNO3

28
Q

Give examples of strong diprotic acids

A

H2SO4

29
Q

Give examples of strong triprotic acids

A

H3PO4

30
Q

Give examples of strong monobasic bases

A

NaOH KOH

31
Q

Give examples of strong diprotic bases

A

Ca(OH)2
Ba(OH)2

32
Q

Give examples of weak monobasic bases

A

ammonia
methylamine

33
Q

Give examples of strong dirpotic bases

A

1,2-diaminoethane

34
Q

Give examples of weak acids

A

mono - ethanoic
di - ethandioic
tri - citiric

35
Q

What is Ka

A

acid dissociation constant
Weak acids and bases only dissocaite partially in water therefore the reaction has an equilibirum dissassociation constant Ka

36
Q

Explain ka

A

We define a new constant as Ka =
Ka = [H+][A-]/[HA]

HA refers to the un-ionised acid molecule, and A- refers to the anion remainder after loss of a proton.
- A large Ka value means that a lot of the acid ionises in solution. (stronger acid)
- A small Ka value means that very little acid ionises in solution. (weaker acid)

37
Q

pKa=

A

pKa = – log Ka

38
Q

the stronger the acid:

A

the bigger Ka
the smaller pKa

39
Q

Basic titration method

A

Standard solution of acid/alkali prepared in volumetric flask

25 cm3 samples taken out with pipette and put into conical flask

Indicator + acid/alkali in conical flask

acid/alkali added from burette until permanent colour change

40
Q

How do you make a standard solution RP1

A
  • mass a weighing bottle/boat
  • add the correct mass of solid
  • pour the contents of the solid into a beaker
  • mass the weighing bottle/boat again (the difference in two recorded masses will provide the exact
    mass of the solid added to the beaker)
  • dissolve the solid in a little distilled water using a stirring rod
  • pour the solution into a volumetric flask using a funnel and stirring rod
  • wash the beaker several times, pouring the washings into the flask
  • top up to the mark carefully (drop-wise at the end)
  • swirl, invert and repeatedly shake to ensure it is homogenous (thoroughly mixed)
41
Q

What is a back titration?

A

Used where reaction between acid and base is slow (e.g. low solubility in water)

React an excess of an acid/base with the acid/base – some is leftover

Titrate the leftover acid/base to see how much leftover

42
Q

What is an indicator?

A

Weak acids which have a different colour to their conjugate bases.
HIn ⇌ H+ + In-
colour 1 ⇌ colour 2

43
Q

How do indicators work?

A

HIn ⇌ H+ + In-
low pH: equilibrium pushed left = colour 1
high pH: equilibrium pushed right = colour 2

44
Q

methyl orange
colour at low ph
range
colour at high pH

A

red
3.2-4.4
organge/yellow

45
Q

phenolphthalein
colour at low ph
range
colour at high pH

A

colourless
8.2-10.0
purple

46
Q

What is a titration curve

A

shows how pH of a solution changes in an acid-base reaction

47
Q

How is the neutralisation point identified

A

a large vertical section therough the equivalence point

48
Q

Define equivalence point

A

The point at which the exact volue of base has been added to just neutralise the acid or vice versa.

49
Q

strong acid-strong base
pH at equivalence:
suitable indicator:

A

7
phenolphthalien/methyl orange

50
Q

strong acid-weak base
pH at equivalence:
suitable indicator:

A

< 7 (4 )
methyl orange

51
Q

weak acid-strong base
pH at equivalence:
suitable indicator:

A

> 7 (9 )
phenolphthalein

52
Q

weak acid-weak base
pH at equivalence:
suitable indicator:

A

depends on the relative strength of th acid and base

53
Q

What is a buffer solution

A

solution that resists changes in pH when small amounts of acid pr alkali are added

NB- pH does change, just not by much

54
Q

Acidic buffer

A

buffers that have a pH lower than 7

55
Q

Basic buffer

A

buffers that have a solution higher than 7

56
Q

What is an acidic buffer made of?

A

mixture of a weak acid and one of its salts (ie HA and A-)

57
Q

What is key in an acidic buffer?

A

the [acid] and [salt] are much higher than the [H+]

58
Q

What are the two routes to make an acidic buffer?
+ how to calculate the pH of the buffer in each route

A

Route 1: mixture of weak acid and one of its salts (use [A-] and [HA] with Ka equation to calculate H+)
Route 2: Mixture oif an excess of weak acid and a strong base
(HA+OH—>A- +H2O to calulate left over HA and formed A- then use Ka)

59
Q

What is a basic buffer made of?

A

a mixture of a weak alkali and one of its salts

60
Q

What is the key in a basic buffer

A

the [base] and the [salt] are much higher than [OH-]

61
Q

What are the two routes to make an basic buffer?

A

Route 1: mixture of weak base and one of its salts
Route 2: mixture of an excess weak base and a strong acid

62
Q

How do buffer solutions work?

A

buffers pH depends on the ratio of [acid]:[salt] or [base]:[salt] so when small amounts of acid (H+) or base (OH-) are added the ratio remains roughly constant and so the pH hardly changes.

63
Q

What happens when you add a little acid to an acidic buffer?

A

HA⇌ H+ + A-
The added H+ is removed by reacting with A- to form more HA.
The [A- ]falls slightly and the [HA] rise slighty but as [HA] & [A-]&raquo_space; [H+] the ratio of [HA]:[A-] remains roughly constant.

64
Q

What happens when you add a little base to an acidic buffer?

A

HA⇌ H+ + A-
The added OH- reacts with H+ and so some HA breaks down to replace that H+

The [A- ]rises slightly and the [HA] falls slighty but as [HA] & [A-]&raquo_space; [H+] the ratio of [HA]:[A-] remains roughly constant.

65
Q

What happens when you add water to an acidic buffer?

A

The ratio of [HA]:[A-] remains constant so pH remains constant

66
Q

How do you calculate when acid is added to an acidic buffer

A
  • calc mol acid added
  • A-+H+–>HA before and after
  • plug into Ka
  • to get new H+
67
Q

How do you calculate when base is added to an acidic buffer

A

-calc mol OH- added
- HA+OH—>A- +H2O before and after
- calc [HA] and [A-] after
- plug into Ka to find H+

same pocess as finding pH of acidic buffer formed via routte 2

Chemistry (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions