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Chemistry OCR A-Level > Chapter 20 > Flashcards

Chapter 20 Flashcards

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1
Q

What do acids release in water?

A

H⁺ ions

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2
Q

What do alkalis release in water?

A

OH⁻ ions

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3
Q

What is the Arrhenius model of acids and bases?

A

1) acids dissociate and release H⁺ ions in aqueous solution
2) alkalis dissociate and release OH⁻ ions in aqueous solution
3) H⁺ ions are neutralised by OH⁻ ions to form water:
H⁺(aq) + OH⁻(aq) –> H₂O)(l)

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4
Q

What is a Brønsted-Lowry acid?

A

proton donor

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5
Q

What is a Brønsted-Lowry base?

A

proton acceptor

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6
Q

What does the Brønsted-Lowry model for acids and bases emphasise?

A

The role of proton transfer between species

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7
Q

What is the equation showing the dissociation of hydrochloric acid, HCl(aq)?

A

HCl(aq) ⇌ H⁺(aq) + Cl⁻(aq)

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8
Q

Is HCl a strong or weak acid?

A

strong

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9
Q

What is a conjugate acid-base pair?

A

two species that can be interconverted by transfer of a proton

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10
Q

What is the formula for the hydronium ion?

A

H₃O⁺

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11
Q

What happens in dissociation?

A

A proton is transferred from an acid to a base

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12
Q

What is required to be present for dissociation to take place?

A

water

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13
Q

What is H₃O⁺(aq) often simplified to?

A

H⁺(aq)

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14
Q

What terms refer to the total number of hydrogen atoms in the acid that can be replaced per molecule in an acid-base reaction?

A

1) monobasic
2) dibasic
3) tribasic

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15
Q

What type of acid is HCl?

A

monobasic

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16
Q

What type of acid is CH₃COOH?

A

monobasic

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17
Q

What type of acid is H₂CO₃?

A

dibasic

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18
Q

What type of acid is H₃BO₃?

A

tribasic

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19
Q

HNO₃(aq) + NaOH(aq) –>

A

NaNO₃(aq) + H₂O(l)

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20
Q

H₂SO₄(aq) + 2NaOH(aq) –>

A

Na₂SO₄(aq) + 2H₂O(l)

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21
Q

H₃PO₄(aq) + 3NaOH(aq) –>

A

Na₃PO₄(aq) + 3H₂O(l)

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22
Q

What do acids react with to form salts?

A

1) metals
2) carbonates
3) metal oxides
4) alkalis

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23
Q

acid + metal –>

A

salt + hydrogen

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24
Q

2H⁺(aq) + Zn(s) –>

A

Zn²⁺(aq) +H₂(g)

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25
Q

Are carbonates acids or bases?

A

bases

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26
Q

acid + carbonate –>

A

salt + water + carbon dioxide

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27
Q

What is an acid neutralised by to form a salt and water only?

A

1) solid metal oxide

2) solid metal hydroxide

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28
Q

acid + base/alkali —>

A

salt + water

29
Q

For any solution at 25°C:

A

1) pH less than 7 shows increasing acidity
2) pH greater than 7 shows increasing alkalinity
3) pH 7 is neutral

30
Q

acid + base –>

acid + alkali –>

A

salt + water

31
Q

2H⁺(aq) + MgO(s) –>

A

Mg²⁺(aq) + H₂O(l)

32
Q

What is the ionic equation of neutralisation?

A

H⁺(aq) + OH⁻(aq) –> H₂O(l)

33
Q

What is pH?

A

Simple numerical scale measuring hydrogen ion concentrations

34
Q

For any solution at 25°C:

A

1) pH < 7 = increasing acidity
2) pH > 7 = increasing alkalinity
3) pH 7 = neutral

35
Q

Does a low value of [H⁺(aq)] match a high or low pH?

A

high

36
Q

Does a high value of [H⁺(aq)] match a high or low pH?

A

low

37
Q

What is the mathematical relationship between pH and [H⁺(aq)]?

A

pH = -log[H⁺(aq)]

38
Q

pH =

A

-log[H⁺(aq)]

39
Q

What is the reverse of pH = -log[H⁺(aq)]?

A

[H⁺(aq)] = 10⁻ᵖᴴ

40
Q

How many more H⁺ ions does a pH of 1 have than a pH of 2?

A

10 times

41
Q

How many more H⁺ ions does a pH of 1 have than a pH of 14?

A

10¹³

42
Q

[H⁺(aq)] =

A

10⁻ᵖᴴ

43
Q

HA(aq) –>

A

H⁺(aq) + A⁻(aq)

44
Q

For a strong acid, what is [H⁺(aq)] equal to?

A

the concentration of the acid, [HA(aq)]

45
Q

For a strong acid, what can the pH be directly calculated from?

A

the concentration of the acid

46
Q

What are the terms strong and weak used to describe?

A

The extent of dissociation of an acid

47
Q

What is Kₐ?

A

the acid dissociation constant

48
Q

What does the general formula HA(aq) –> H⁺(aq) + A⁻(aq) show?

A

The dissociation of any weak acid, HA

49
Q

How is the acid dissociation constant Kₐ calculated?

A

Kₐ = [H⁺(aq)] [A⁻(aq)] / [HA(aq)]

50
Q

What are the units of the acid dissociation constant, Kₐ?

A

mol dm⁻³

51
Q

Is the Kₐ expression used for strong or weak acids?

A

weak

52
Q

The larger the numerical value of Kₐ, the further the equilibrium is to which side?

A

right

53
Q

pKₐ =

A

-logKₐ

54
Q

What is the reverse of pKₐ = -logKₐ?

A

Kₐ = 10⁻ᵖᴷᵃ

55
Q

The stronger the acid, the ___ the Kₐ value and the ___ the pKₐ value.

A

1) larger

2) smaller

56
Q

The weaker the acid, the ___ the Kₐ value and the ___ the pKₐ value.

A

1) smaller

2) larger

57
Q

When a strong acid HA completely dissociates, [H⁺(aq)] =

A

[HA(aq)]

58
Q

When a weak acid partially dissociates, [H⁺(aq)] ≠

A

[HA(aq)]

59
Q

What does [H⁺(aq)] depend upon?

A

1) the concentration of the acid, [HA(aq)]

2) the acid dissociation constant Kₐ

60
Q

How can you determine the Kₐ for a weak acid experimentally?

A

1) preparing a standard solution of the weak acid of known concentration
2) measuring the pH of the standard solution using a pH meter

61
Q

Is water an acid or a base?

A

both

62
Q

H₂O(l) + H₂O(l) ⇌

A

H₃O⁺(aq) + OH⁻(aq)

63
Q

What is Kᵥᵥ?

A

ionic product of water

64
Q

Kᵥᵥ =

A

[H⁺(aq)] [OH⁻(aq)]

65
Q

What is the value of Kᵥᵥ at 298K (25°C)?

A

1.00 x 10⁻¹⁴ mol² dm⁻⁶

66
Q

What is the significance of Kᵥᵥ having a value of 1.00 x 10⁻¹⁴ mol² dm⁻⁶ at 25°C?

A

sets up the neutral point in the pH scale

67
Q

What is an alkali?

A

A soluble base that releases OH⁻ ions in aqueous solution

68
Q

What can the pH of a strong base be calculated from?

A

1) concentration of the base

2) ionic product of water Kᵥᵥ

Chemistry OCR A-Level (28 decks)

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