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Chemistry Leaving Cert > Acids and Bases* > Flashcards

Acids and Bases* Flashcards

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1
Q

What is an Arrhenius Acid?

A

a substance that dissociates in water to produce H+ ions.

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2
Q

What is an Arrhenius Base?

A

a substance that dissociates in water to produce OH- ions.

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3
Q

What is a Bronsted Lowry Acid?

A

is a proton (H+) donor

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4
Q

What is a Bronsted Lowry Base?

A

is a proton (H+) acceptor

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5
Q

What is neutralisation?

A

the reaction between an acid and a base, forming a salt and water. (acid + base => salt + water)

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6
Q

What is formed by neutralisation and why?

A

Water and a salt. Salt is formed when the H of an acid is replaced by a metal.

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7
Q

Why is salt formed by neutralisation?

A

Salt is formed when the H of an acid is replaced by a metal.

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8
Q

What is the formula for neutralisation (words not symbols)?

A

(acid + base => salt + water)

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9
Q

What is a conjugate acid?

A

a conjugate acid is formed when a base accepts a proton

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10
Q

What is a conjugate base?

A

a conjugate base is formed when an acid donates a proton.

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11
Q

What is a conjugate pair?

A

an acid and a base that differ by a proton

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12
Q

What is a primary standard?

A

Primary standard is a substance of high Mr (Relative Molecular Mass) which can be obtained in a pure stable soluble form so that it can be weighed out and dissolved in water to give a solution of accurately known concentration.
(Know why high Mr matters)

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13
Q

What is titration?

A

A laboratory procedure where a measured volume of one solution is added to a known volume of another solution until the reaction is complete.
(concentration of one solution known accurately at start)
(indicator used to show by colour change when reaction is complete)

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14
Q

Give the pH equation for titration

A

pH = -log [H+]
pH < 7 acid
pH = 7 neutral
pH > 7 base

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15
Q

Give the Kw equation?

A 
Kw = [H+].[OH-]
([H+] + the square root of Kw)
Also remember     (at 25 degrees celsius)
Kw = 1x10 -14 (-14 like a power)
so [H+] = 1x10 -7 (-7 like a power)
and pH = 7
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16
Q

Why is it helpful that primary standard can be obtained in a pure stable soluble form

A

so that it can be weighed out and dissolved in water to give a solution of accurately known concentration.

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17
Q

what is known at the start of a titration?

A

(concentration of one solution known accurately at start)

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18
Q

What is used to show colour change when reactioni is complete in a titration?

A

(indicator used to show by colour change when reaction is complete)

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19
Q

What is a strong acid good for? + formula

A

It is a good proton donor or (is fully dissociated into ions in dilute aqueous soln.)
[H+] = [acid] HCl
[H+] = 2x[acid] H2SO4 etc

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20
Q

What is a weak acid bad at?

A

A weak acid is a poor proton donor or (slightly dissociated into ions in dil. aq. soln.)
[H+] = square root of Ka x Macid

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21
Q

What is a strong base good for? + formula

A

Is a good proton acceptor or (one which is fully dissociated into ions in dilute aqueous solution)
[OH-] = [base] NaOH
[OH-] = 2x [base] Ca(OH)2 etc

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22
Q

What is a weak base bad at?

A

A weak base is a poor proton acceptor or one which is slightly dissociated in dil. aq. soln.
[OH-] = square root of Kb x Mbase

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23
Q

What is an acid base indicator?

A

a substance that changes colour according to the pH of the solution it is in.
(equilibrium Hln H+ =+ In-)

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24
Q

What colour is Methyl orange in acid? Why?

A

Red - lower pH

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25
Q

What colour is Methyl orange in base? Why?

A

Yellow - higher pH

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26
Q

What colour is phenolphthalein in acid? Why?

A

colourless - lower pH

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27
Q

What colour is phenolphthalein in base? Why?

A

pink - higher pH

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28
Q

What is the pH range of phenolphthalein?

A

pH 8 - 11

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29
Q

What is the pH range of Methyl orange?

A

pH 3-5

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30
Q

What colour is litmus in acid? Why?

A

red - lower pH

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31
Q

What colour is litmus in base? Why?

A

blue - higher pH

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32
Q

What is the pH range of litmus?

A

pH 5-8

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33
Q

Why might you not use litmus?

A

not as reliable as others for accurate work

34
Q

Which indicator do you use for strong acid/strong base?

A

Methyl orange/phenolphthalein/litmus (though litmus is not as reliable as others for accurate work)

35
Q

Which indicator do you use for strong acid/weak base?

A

methyl orange

36
Q

Which indicator do you use for weak acid/strong base?

A

phenolphthalein

37
Q

Which indicator do you use for weak acid/weak base?

A

none

38
Q

What is a solution?

A

A solution is a completely perfect mixture of a solute and a solvent, where the particles of the solute are uniformly distributed throughout the solvent i.e. the mixture is homogenous.

39
Q

What is homogenous?

A

where the particles of the solute are uniformly distributed throughout the solvent

40
Q

What is concentration?

A

The concentration of a solution is the amount of solute that is dissolved in a given volume of solution

41
Q

What is molarity?

A

The molarity of a solution is the number of moles of solute per litre of solution

42
Q

What are acids?

A

substances that turn blue litmus red and react with metals like Zinc, thus releasing hydrogen gas

43
Q

What is a base that dissolves in water known as?

A

an alkali

44
Q

What is an alkali?

A

a water soluble base

45
Q

If sodium hydroxide in an alkali what is sodium hydroxide solution?

A

alkaline

46
Q

What is alkaline?

A

having the properties of a water soluble base or containing a water soluble base

47
Q

what are bases?

A

Substances which turn red litmus blue

48
Q

What are examples of bases?

A

Sodium hydroxide (NaOH), Sodium Carbonate (Na2CO3) and ammonia (NH3) are all examples of bases

49
Q

what are examples of acids?

A

Hydrochloric acid (HCl), Sulfuric acid (H2SO4) and Nitric acid (HNO3) are all examples of strong acids

50
Q

give examples of everyday acids

A

Vinegar, lactic acid in milk as it goes sour, citrus fruits & hydrochloric acid in the stomach necessary for digestion and killing micro organisms

51
Q

give examples of lab acids

A

Hydrochloric Acid (HCl), Sulfuric Acid (H2SO4) and Nitric Acid (HNO3)

52
Q

give examples of lab bases

A

Sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and ammonia (NH3)

53
Q

give examples of everyday bases

A

oven cleaner, bleach, caustic soda, toothpaste & washing up liquid.

54
Q

Monobasic acids

A

Refers to an acid which donates on proton per molecule e.g. HCl and HNO3

55
Q

Dibasic acids

A

Refers to an acid which donates 2 protons per molecule e.g. H2SO4

56
Q

Tribasic acids

A

Refers to an acid which donates 3 protons per molecule e.g. H3PO4

57
Q

What is the Arrhenius theory of an acid?

A

He suggested that an acid is a substance which dissociates in aqueous solution to form
H+ ions : HX(aq) -> H+ + X-
brackets in small with small brackets

58
Q

What are the limitations of Arrhenius’ theory of an acid?

A
  1. It is limited to reactions taking place in water

2. H+ ions does not exist in water on its own (Joins with a H2O molecule an forms H3O+)

59
Q

What do bases do to acids?

A

neutralise them

60
Q

What is the Arrhenius theory of a base?

A

A base is a substance that dissociates in aqueous solution to produce OH- ions.
NaOH(aq) -> Na+ +OH-
brackets in small with small brackets

61
Q

What are the limitations to the Arrhenius theory of a base?

A
  1. It is limited to reactions taking place in water, other solvents like methylbenzene or liquid ammonia were exceptions.
  2. Substances such as NH3 would not be classified as bases (do not produce OH- ions)
62
Q

According to Arrhenius how would an acid react with a base i.e. neutralisation reaction?

A

In solution the acid molecules dissociates and forms H+ ions.
The base molecules dissociates and form OH- ions.
The H+ ions and OH- ions react and form H2O. Note: A salt is mostly formed in such reactions.

63
Q

What is a neutralisation reaction?

A

A reaction in which an acid and a base react to form a salt and water

64
Q

What is a common example of a neutralisation reaction?

A

When we consume an indigestion tablet to combat excess stomach acid. 2HCl + Mg(OH)2 -> MgCl2 + 2H2O

65
Q

What is an acid? (not definition)

A

An acid is a proton donor (H+) therefore a strong acid is a strong proton donor

66
Q

What is a base? (not definition)

A

A base is a proton acceptor

67
Q

What are the advantages of the Bronsted Lowry’s theory?

A

Does not just deal with reactions in water

e.g. HCl + NH3 -> NH4Cl

68
Q

What is a conjugate base?

A

Species formed when an acid has donated a proton: HCl -> Cl- (acid) (conjugate base)

69
Q

What are more examples of conjugate base formations

A

HNO3 > NO3 -

H2S > HS-

70
Q

What is a strong acid?

A

This is an acid which dissociates fully into ions in an aqueous solution e.g. HCl –> H+ + Cl-

71
Q

What does every HCl molecule break up into?

A

ions

72
Q

What is a weak acid?

A

This is an acid which only slightly dissociates into ions in an aqueous solution e.g. CH3COOH (aq) –> CH3COO- + H+

73
Q

Do many weak acid molecules dissociate?

A

Very few of these acid molecules dissociates or break up into ions

74
Q

Why is H2SO4 considered to be a strong acid?

A

This acid fully dissociates into ions when in an aqueous solution. It has a great tendency to break/give protons

75
Q

Explain why strong acids form weak conjugate bases.

A

H2SO4 -> HSO4 - (strong acid) (weak conjugate base)
A strong acid such as sulphuric acid readily donates a proton and forms a conjugate base HSO4 -
The conjugate base i.e. HSO4 - is a weak base as it does not readily accept a proton

76
Q

Show that a conjugate base H2SO4 can itself act as an acid

A

The H2SO4 loses a proton and forms the conjugate base HSO4 -.
The conjugate base HSO4- then donates a proton i.e. behaves as an acid (SO4 (2-))
*2- as a power in small

77
Q

What is a conjugate acid?

A

Species formed when a base has accepted a H+ proton: NH3 > NH4+ (base) (conj. Acid)

78
Q

Define conjugate acid/bond pair

A

These are 2 substances which differ by an H+ or a proton. E,g, HCl <> Cl-

79
Q

What is an amphoteric substance?

A

This is a substance which can behave as an acid or a base depending on what it reacts with

e. g. 1) H2O behaves as a base (accepts a proton)
e. g. 2) H2O molecules loses a proton (behaves as an acid)

80
Q

What does the acidity of a solution depend on?

A

The concentration of H+ ions in the solution

H+ concentration > more acidic the solution is

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