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Chemistry > U2AoS1 - Water > Flashcards

U2AoS1 - Water Flashcards

1
Q

Where is freshwater found on earth?

A

Ice and groundwater

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1
Q

How much water is readily available for consumption?

A

1% is readily available

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2
Q

Where is most water contained on earth?

A

Oceans

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3
Q

Define Potable

A

Water that is safe to drink

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4
Q

Examples of Potable water sources

A
  • flowing water through protected catchments
  • groundwater
  • rain
  • desalination
  • reservoirs
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5
Q

Water

A

The only substance on earth that naturally occurs on earth in all three states.

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6
Q

States of Matter

A
  • solid
  • liquids
  • gas
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7
Q

What are Group 16 Hydrides?

A

Hydrogen covalently bonded to group 16 elements

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8
Q

Boiling points moving down group 16

A

Increases with increasing molecule size and number of dispersion forces.

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9
Q

Chemical structure of water

A

Water is a bent, polar molecule with strong hydrogen bonding between molecules.
Forms up to 4 intermolecular hydrogen bonds

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10
Q

High boiling point of water

A

Strong hydrogen bonds require a large amount of energy to break when changing states.

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11
Q

Expands on freezing

A

Compares density of solid ice and liquid water

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12
Q

Density of solid ice

A

Each water molecule bonds with 4 other water molecules forming a tetrahedral lattice arrangement
- creates empty space in the structure as the molecules are further away.

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13
Q

Density of Liquid water

A

Molecules are randomly arranged, allowing strong hydrogen bonds that pull the water molecules closer together
Liquid water is more dense than ice.

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14
Q

What is heat capacity?

A

The relationship between heat (thermal energy) absorbed by a substance and its temperature change
- capacity to store heat

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15
Q

What is specific heat capacity

A

Amount of energy required in Joules, to raise the temperature of 1g of the substance by 1 degree.

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16
Q

Specific heat capacity of water

A
  • high value of 4.18Jg-1
  • Takes 4.18 Joules of heat energy to increase the temperature of 1 gram of water by 1 degree
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17
Q

Why does water have a high specific heat capacity?

A

Strong hydrogen bonds between water molecules are able to absorb a large amount of chemical anergy before increasing temperature

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18
Q

Relationship of heat capacity

A

The more effectively a substance can store heat energy, the higher the specific heat capacity.

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19
Q

Heat energy is calculated by

A

q = m x c x difference in T

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20
Q

Joules to Kilojoules

A

1000J = 1KJ

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21
Q

What is latent heat of vaporisation?

A

amount of energy required to convert 1 mole of a substance from liquid state to gaseous state at the boiling point of the substance.

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22
Q

Unit of latent heat

A

KJmol-1

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23
Q

Latent heat of vaporisation of water

A

44.0
High due to the strong hydrogen bonds between water molecules which are able to absorb a large amount of thermal energy before changing states.

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24
Q

Latent heat

A

energy absorbed by a fixed amount of substance as it changes state (fusion/vaporisation)

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25
Q

Latent heat of fusion

A

amount of energy required to convert 1 mole of a substance from solid state to liquid state at the boiling point of the substance.

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26
Q

Formula for calculating latent heat

A

q = n x l
q is in KJ

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27
Q

Why is latent heat important?

A

Cooling system (sweat)
Water cycle (longevity)

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28
Q

Why is the specific heat capacity of water greater than that of ethanol?

A
  • polar molecules larger than water have smaller heat capacity
  • many more molecules of water in 1.0g
  • able to absorb more heat energy without changing temperature as more energy goes into breaking bonds.
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29
Q

What are the properties of acids?

A
  • sour
  • turns blue litmus red
  • corrosive, reacts with bases
  • conducts electricity in a solution
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30
Q

Why can acids and bases conduct electricity?

A

Contains charged particles that can move freely.

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31
Q

What are strong acids?

A

HCl, H2S04, HNO3

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32
Q

Hydrochloric acid

A

HCl - strong acid

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33
Q

Sulfuric acid

A

H2SO4 - strong acid

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34
Q

Nitric acids

A

HNO3

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35
Q

Ethanoic acids

A

CHCOOH - weak acid

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36
Q

Carbonic acid

A

H2CO3 - weak acid

37
Q

Phosphoric acid

A

H3PO4 - weak acid

38
Q

Properties of bases

A
  • bitter
  • turn red litmus blue
  • slippery
  • conduct electricity in solution
39
Q

What are strong bases?

A

metal hydroxides

40
Q

What are strong bases

A

ammonia (NH3)
sodium carbonate (NaCO3)

41
Q

Magnesium carbonate

A

mg(OH2) - strong base

42
Q

What is the pH scale?

A

Measures how acidic a substance is

43
Q

Acidity

A

A measure of the concentration of H+ ions or hydronium ions in solution

44
Q

What is a proton?

A

Hydrogen ion H+

45
Q

Acid

A

substance that donates a proton to a base - proton donor

46
Q

Base

A

substance that accepts a proton from an acid - proton acceptor

47
Q

Acid - base reaction

A

Involves the transfer of a proton from an acid to a base.

48
Q

What is important to remember with any weak acid/base reaction

A

Double arrows

49
Q

Conjugate acid-base pair

A

Molecules or ions which differ by one H+ proton

50
Q

Conjugate acid

A

contains one more proton than the base

51
Q

conjugate base

A

contains one less proton than the acid

52
Q

Amphiprotic substances

A

substances which can behave as either acids or bases depending on what it is reacting with.
Donate and accept protons

53
Q

Examples of amphiprotic substances

A

water, Hco3, Hso4-

54
Q

Which part of CH3COOH is the acidic section?

55
Q

Polyprotic acids

A

can donate more than one ion

56
Q

Examples of polyprotic acids

A

sulfuric acid (H2SO4) diprotic donate two
phosphoric acid (H3PO4) triprotic donate three
- only first one ionizes completely.

57
Q

Ionisation

A

substance reacts with water to produce ions.
Ions dissolve in the water (form ion dipole bonds)
Acid + water

58
Q

Ionisation is also known as

A

Hydrolysis reaction

59
Q

Ionisation of strong acids

A

completely
water accepts protons, acts as base
produces hydronium ions

60
Q

Ionisation of weak acids

A

partially ionise

61
Q

Ionisation of weak base

A

production of hydroxide ions represents base solution
water donates proton, acting as an acid

62
Q

Dissociation

A

A solid ionic compound dissolves in water and the ionic bonds break separating into cations and anions

63
Q

Dissociation followed by hydrolysis

A

Some ions will also undergo hydrolysis with water after dissociation

64
Q

General rule for ionisation and dissociation

A

Most acids ionise in water, most bases dissociate in water

65
Q

Strength

A

How readily an acid or base donates/accepts protons
Type of acid or base

66
Q

Strength of strong acids

A
  • readily donates protons
  • ionise completely in water to produce hydronium ions
67
Q

Strength of weak acids

A
  • do not readily donate protons
  • ionise partially producing hydronium ions
68
Q

Strength of strong base

A

dissociate completely in water to produce hydroxide ions

69
Q

Strength of base

A

Ionize partially with water to produce hydroxide ions

70
Q

Concentration

A

how much of the acid/base is dissolved in a given volume of a solution

71
Q

Concentrated solution

A

Contains a large amount of acid/base in a given amount of solution

72
Q

Dilute solution

A

contains a small amount of acid/base in a given amount of solution

73
Q

Unit for concentration

A

molarity amount of mol per volume
m/L

74
Q

How to read molarity

A

The higher the value the higher the concentration

75
Q

Reactions of acids+base

A
  1. acid + metal carbonate
  2. acid + metal hydrogen carbonate
  3. acid + metal hydroxide
  4. acid + metal
76
Q

Acid with metal carbonate

A

Metal carbonates - weak bases that neutralise acids
either soluble or insoluble
acid + metal carbonate = ionic salt + water + CO2

77
Q

Important to remember when reacting acids with metal carbonate

A

When added to water, a soluble metal carbonate will dissociate while insoluble metal carbonate will stay as a solid

78
Q

Acid with metal hydrogen carbonate

A

weak bases that neutralise acids
Acid + MHC = IS + H20 + CO2

79
Q

Acid with metal hydroxide

A

strong base
soluble/insoluble
Acid + MH - ionic salt + water
The h+ ions from the acid react with the OH- ions from the base to produce water which has a neutral pH, hence neutralisation reaction

80
Q

Important to remember about acid + metal hydroxide

A

writing chemical formula with acetate ion (CH2COO-) put chc300 first

81
Q

Acid + metal

A

Ionic salt + hydrogen gase
Not neutralisation, no water produced

82
Q

Pure water

A

Amphiprotic, undergoes self ionisation to a small extent

83
Q

Indicator

A
  • substance which changes colour to show acidity/basicity
    natural, commercial
    some provide pH range, others actual value
84
Q

Ph range

A

low accuracy, precision

85
Q

Acucuracy

A

experimental value is close to true value

86
Q

Precision

A

how close measurements are to each other

87
Q

Litmus paper

A

natural
detects if a substance is acidic/basic
red = acidic
blue = basic

88
Q

Indicator

A

pH value
increases accuracy/preciision
Universal indicator

89
Q

pH meter

A

specific quantitative pH, most accurate, precise

Chemistry (8 decks)

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