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IB Chemistry > Reactivity 3.1 > Flashcards

Reactivity 3.1 Flashcards

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1
Q

Svante Arrheniu’s theory of acids

A

acidic substances dissociated in aqueous solutions to produce hydrogen ions

Basic substances dissociated in aqueous solutions to produce hydroxide ions

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2
Q

Bronsted-Lowry acid

A

hydrogen ion (proton) donor

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3
Q

Bronsted-Lowry base

A

hydrogen ion (proton) acceptor

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4
Q

What is a hydrogen ion?

A

Hydrogen atom that has lots its electron

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5
Q

Why is the hydrogen ion basically a proton?

A

Very small and large charge density

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6
Q

What happens when Bronsted-Lowry acid molecules mix with water?

A

They ionise
HX -> H+ + X-

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7
Q

What is the hydrogen ion attracted to?

A

Water molecules, forming the hydronium ion

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8
Q

What are the chemical properties of acids in aqueous solution due to?

A

Presence of hydronium ions

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9
Q

Conjugate-acid base pairs

A

Species that differ by one proton (acid written first)

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10
Q

Amphiprotic substances

A

substances that are capable of both accepting and donating a proton depending on reaction conditions

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11
Q

When does water act as a base

A

when reacting with a stronger acid

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12
Q

When does water act as an acid

A

when reacting with a stronger base

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13
Q

Amphoteric substances

A

Used to describe substances that can react as acid or basics

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14
Q

Example of amphoteric substances

A

ZnO

ZnO + 2H+ -> Zn2+ + H2O

Zn + H2O + OH- -> Zn(OH)4)2-

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15
Q

pH scale

A

measured scale that extends from 0-14 that show relative acidity, using a logarithmic scale

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16
Q

what is the midpoint of the pH scale

A

at 25 degrees, 7

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17
Q

Formula for pH

A

-log[H3O+]

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18
Q

Formula for [H3O+] from pH

A

[H3O+] = 10-pH

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19
Q

For strong monoprotic acids [HA] =

A

[H3O+]

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20
Q

Significant figures in the [H3O+] become

A

DP in pH

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21
Q

Self-ionisation of water

A

As it is an amphiprotic susbtance, it can act as an acid or a base depending on the cirumstances. Therefore, it can react with itself

H2O + H2O -> H3O+ + OH-

As water is a poor conductor of electricity, we can assert that there are very few of these ions formed

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22
Q

Ion product constant (Kw)

A

[H3O+] x [OH-] = 10^-14 mol2 dm-6 at 25 degrees

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23
Q

What is the ion product constant true for?

A

All aqueous solutions

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24
Q

Strong acids

A

Virtually completely ionise in aqueous solution

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25
Q

Weak acids

A

Partially ionise in solution(<100%)

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26
Q

Strong acids example

A

HCl
HBr
HI
HNO3
H2SO4

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27
Q

Weak acids

A

Acetic/ethanoic acid: CH3COOH

H2CO3

H3PO4

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28
Q

What is used to express the ionisation of weak acids?

A

A double arrow, as they exist in equilibrium. The resulting solution is a mixture of both reactants and products, and the concentration of hydronium ions is equal to the concentration of the conjugate bate (ignoring self-ionisation of water)

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29
Q

Strong base

A

readily accepts a hydrogen ion

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30
Q

Strong base examples

A

OH-
O2-
LiOH
NaOH
KOH

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31
Q

weak bases

A

partially ionise in water to produce hydroxide ionswea

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32
Q

weak base examples

A

ammonia: NH3
ethylamine: CH3CH2NH2
carbonate ion: CO32-
C2H5NH2

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33
Q

The strength of a conjugate base is inversely..

A

proportionate to that of its acid

e.g. HCl (strong base) has a very weak conjugate base (Cl-)

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34
Q

Strong acids (100% deionised in aqueous solution) have a…

A

weak base (negligible tendency to be protonated in aqueous solution)

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35
Q

Weak acids (exist in a solution in a mixture of HA, A- and H3O+) make

A

Weak bases (moderate tendency to be protonated in aqueous solution

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36
Q

Very weak acids (neglible tendency to dissociate) make

A

strong bases (100% protonated in aqueous solution)

37
Q

Concentrated

A

Large amount of solue dissolved in a solvent

38
Q

Dilute

A

Small amount of solute dissolved in a solvent

39
Q

Distinguishing between strong and weak acids/bases relies on the fact that:

A

Strong acids and bases have a greater extent of ionisation in solution, so their resulting solution with have a greater concentration of ions.

This property can be used to distinguish between them, if solutions of the same concentration are compared at the same temperature

40
Q

Tests that can be done to compare strong/weak acids/bases

A

Electrical conductivity: depends on concentration of ions. Stronger acids/bases have a higher conductivity than weak acids/bases

Rate of reaction: reactions of acids with bases depend on the conentration of H+ ions. A faster rate of reaction will occur with a higher concentration, so strong acids will have a faster reaction

pH: measure of H3O+ concentration. A strong acid will have a lower pH than a weak acid of the same molar concentration

41
Q

Monoprotic

A

Have one ionisable hydrogen atom per molecule

42
Q

Diprotic

A

Have two ionisable hydrogen atoms per molecules

43
Q

Triprotic

A

Has two ionisable hydrogen atoms per molecules; thus, ionises and reacts with water in three stages

44
Q

What happens when an acid is added to a metal (hydr)oxide base

A

the properties of both the acid and the base are “lost”

i.e. the acid is neutralised by the base

45
Q

Parent acids and bases

A

The original acids and bases that a salt (produced in a neutralisation) reaction came from

46
Q

How to identify parent acids and bases

A

Split salt into cation and anion. Add hydroxide ions to the cation (making parent base) and protons to the anion (parent acid)

47
Q

How can the unknown concentration of an acid/base be determined?

A

By an acid/base titration using a standard solution

48
Q

Equivalence point

A

Point at which the acid and base are in equal proportions and have neutralised each other i.e. neither reactant is in excess / reactants are present according to mole ratio

49
Q

Describe pH titration curve of a strong acid being added to a strong base

A
  • Starts at high pH (i.e. 13)
    As more volume of acid is added, the pH slowly descreases.
    At point of inflection, the pH plummets, passing the equivalence point
    Will eventually reach a pH of ~1
50
Q

End point

A

Moment of colour change (where both colours of indicator are present)

51
Q

Burette

A

Used to deliver volumes accurately

52
Q

Titre

A

volume delivered from the burette

53
Q

volumetric pipette

A

used for accurate transfer of fixed volumes

54
Q

Aliquot

A

Known volume delivered from the pipette

55
Q

Titration

A

Process of mixing the reactants in a volumetric analysis until they are present in the exact mole ratio represented by the balanced equation. This is a procedure for accurately determining the concentration of an unknown solution

56
Q

Standard solution

A

Solution of accurately known concentration

57
Q

Traits of primary standard

A

Readily available in pure form
Have a known formula
Be easy to store without deteriorating or reacting with the atmosphere

E.g. Sodium carbonate

58
Q

What should a volumetric flask be rinsed with, just prior to use?

A

Deionised wter

59
Q

How is the primary standard transferred to the volumetric flask?

A

using a funnel

60
Q

what error will occur if not all the primary standard is transferred into the volumetric flask?

A

Concentration of standard solution will be lower than the calculated concentration, as less mass (moles) would have been transferred than calculated

61
Q

What volume would’ve been dispensed if the burette is emptied completely?

A

an unknown volume, greater than 50,00cm3

62
Q

Uncertainty for burette reading

A

0.05H

63
Q

how many decimal places must be recorded for a burette reading?

A

2

64
Q

Formula for titre volume

A

V(titre) = V(final) - V(initial)

65
Q

What should burette be rinsed with just prior to us?

A

The solution with which it is to be filled

66
Q

how many dp are pipettes accurate to?

A

2

67
Q

what are pipettes rinsed with just prior to use?

A

the solution with which they are to be filled

68
Q

Why is the hand holding the pipette close to the end?

A

support pipette and reduce chance of it breaking

69
Q

Where to never pipette from?

A

volumetric flask

70
Q

why is the standard solution poured into a beaker and the aliquot taken from the beaker?

A

to avoid contamination of the stock of standard solution

71
Q

what should the beaker be rinsed with jut prior to pipetting?

A

the standard solution

72
Q

what error would occur if the beaker was rinsed with water just prior to pipetting?

A

the solution in pipette would be diluted -> less titre volume added

73
Q

Where does the aliquot get transferred to?

A

Conical flask

74
Q

What quantities are known about the solution in the conical flask?

A

concentration and volume

75
Q

What should conical flask be rinsed with just prior to use?

A

deionised water

76
Q

where is indicator placed in titration?

A

conical flask

77
Q

when do you stop adding solution from the burette?

A

when the indicator changes colour

78
Q

why does the indicator change colour?>

A

addition of acid from burette changes pH of solution; and colour of indicator depends on pH

79
Q

What can the tip of the burette and the sides of the conical flask be rinsed down with?

A

Water, as it won’t affect the moles

80
Q

Concordant meaning

A

Within uncertainty

81
Q

Note about end point v.s. equivalence point

A

as the indicator is an acid/base itself, a slight excess of the solution needs to be added past the equivalence points to get to the end point. Hence, the end point will always be an approximation of equivalence point

82
Q

Titration question to find concentration of the aliquot

A

Balanced chemical equation

Averafge titre volume

Average amount of moles used (in titre)

Moles of aliquot solution used to neutralise titre (according to balanced chemical equation)

Concentration of aliquot, using c = n/V

83
Q

How to make a primary solution?

A

Weigh solids + weight bottle
Add weighed solid crystals to the flask through a funnel
Reweigh the empty weighing bottle + lid (i.e. weigh by difference)

Add deionised water until the flask is 1/3 full. Swirl the flask to dissolve the solute. Add water until 1cm below the etched mark.

Add hte final amount of water using a dropping pipette, until the bottom of the meniscus sits at the edged line. Add lid and invert flask to ensure even distribution of solute

84
Q

Alkalis

A

bases that provide OH- as the only anion inn aqueous soluton

85
Q

alkalis examples

A

NaOH
KOH

86
Q

Strong alkalis

A

Alkalis that are soluble and give rise to a high concentration of OH- ions.

87
Q

Weak alkalis

A

Less soluble alkalis that only give rise to a few hydroxide ions in solution

88
Q

Do all alkalis contain hydroxide ions?

A

No, but they all give rise to hydroxide ions in aqueous solutions

e.g. NH3 + H20 -> NH4+ + OH- (therefore alkali)

IB Chemistry (10 decks)

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