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Chemistry > U2AoS1 - Water > Flashcards

U2AoS1 - Water Flashcards

(90 cards)

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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
Latent heat
energy absorbed by a fixed amount of substance as it changes state (fusion/vaporisation)
25
Latent heat of fusion
amount of energy required to convert 1 mole of a substance from solid state to liquid state at the boiling point of the substance.
26
Formula for calculating latent heat
q = n x l q is in KJ
27
Why is latent heat important?
Cooling system (sweat) Water cycle (longevity)
28
Why is the specific heat capacity of water greater than that of ethanol?
- 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.
29
What are the properties of acids?
- sour - turns blue litmus red - corrosive, reacts with bases - conducts electricity in a solution
30
Why can acids and bases conduct electricity?
Contains charged particles that can move freely.
31
What are strong acids?
HCl, H2S04, HNO3
32
Hydrochloric acid
HCl - strong acid
33
Sulfuric acid
H2SO4 - strong acid
34
Nitric acids
HNO3
35
Ethanoic acids
CHCOOH - weak acid
36
Carbonic acid
H2CO3 - weak acid
37
Phosphoric acid
H3PO4 - weak acid
38
Properties of bases
- bitter - turn red litmus blue - slippery - conduct electricity in solution
39
What are strong bases?
metal hydroxides
40
What are strong bases
ammonia (NH3) sodium carbonate (NaCO3)
41
Magnesium carbonate
mg(OH2) - strong base
42
What is the pH scale?
Measures how acidic a substance is
43
Acidity
A measure of the concentration of H+ ions or hydronium ions in solution
44
What is a proton?
Hydrogen ion H+
45
Acid
substance that donates a proton to a base - proton donor
46
Base
substance that accepts a proton from an acid - proton acceptor
47
Acid - base reaction
Involves the transfer of a proton from an acid to a base.
48
What is important to remember with any weak acid/base reaction
Double arrows
49
Conjugate acid-base pair
Molecules or ions which differ by one H+ proton
50
Conjugate acid
contains one more proton than the base
51
conjugate base
contains one less proton than the acid
52
Amphiprotic substances
substances which can behave as either acids or bases depending on what it is reacting with. Donate and accept protons
53
Examples of amphiprotic substances
water, Hco3, Hso4-
54
Which part of CH3COOH is the acidic section?
COOH
55
Polyprotic acids
can donate more than one ion
56
Examples of polyprotic acids
sulfuric acid (H2SO4) diprotic donate two phosphoric acid (H3PO4) triprotic donate three - only first one ionizes completely.
57
Ionisation
substance reacts with water to produce ions. Ions dissolve in the water (form ion dipole bonds) Acid + water
58
Ionisation is also known as
Hydrolysis reaction
59
Ionisation of strong acids
completely water accepts protons, acts as base produces hydronium ions
60
Ionisation of weak acids
partially ionise
61
Ionisation of weak base
production of hydroxide ions represents base solution water donates proton, acting as an acid
62
Dissociation
A solid ionic compound dissolves in water and the ionic bonds break separating into cations and anions
63
Dissociation followed by hydrolysis
Some ions will also undergo hydrolysis with water after dissociation
64
General rule for ionisation and dissociation
Most acids ionise in water, most bases dissociate in water
65
Strength
How readily an acid or base donates/accepts protons Type of acid or base
66
Strength of strong acids
- readily donates protons - ionise completely in water to produce hydronium ions
67
Strength of weak acids
- do not readily donate protons - ionise partially producing hydronium ions
68
Strength of strong base
dissociate completely in water to produce hydroxide ions
69
Strength of base
Ionize partially with water to produce hydroxide ions
70
Concentration
how much of the acid/base is dissolved in a given volume of a solution
71
Concentrated solution
Contains a large amount of acid/base in a given amount of solution
72
Dilute solution
contains a small amount of acid/base in a given amount of solution
73
Unit for concentration
molarity amount of mol per volume m/L
74
How to read molarity
The higher the value the higher the concentration
75
Reactions of acids+base
1. acid + metal carbonate 2. acid + metal hydrogen carbonate 3. acid + metal hydroxide 4. acid + metal
76
Acid with metal carbonate
Metal carbonates - weak bases that neutralise acids either soluble or insoluble acid + metal carbonate = ionic salt + water + CO2
77
Important to remember when reacting acids with metal carbonate
When added to water, a soluble metal carbonate will dissociate while insoluble metal carbonate will stay as a solid
78
Acid with metal hydrogen carbonate
weak bases that neutralise acids Acid + MHC = IS + H20 + CO2
79
Acid with metal hydroxide
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
Important to remember about acid + metal hydroxide
writing chemical formula with acetate ion (CH2COO-) put chc300 first
81
Acid + metal
Ionic salt + hydrogen gase Not neutralisation, no water produced
82
Pure water
Amphiprotic, undergoes self ionisation to a small extent
83
Indicator
- substance which changes colour to show acidity/basicity natural, commercial some provide pH range, others actual value
84
Ph range
low accuracy, precision
85
Acucuracy
experimental value is close to true value
86
Precision
how close measurements are to each other
87
Litmus paper
natural detects if a substance is acidic/basic red = acidic blue = basic
88
Indicator
pH value increases accuracy/preciision Universal indicator
89
pH meter
specific quantitative pH, most accurate, precise

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