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Chemistry > Elements Of The Sea > Flashcards

Elements Of The Sea Flashcards

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1
Q

What is the atom economy equation

A

Mr useful products / Mr useful reactants x 100

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2
Q

When is the big number in an equation used

A

In atom economy

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3
Q

How do you find molecular formula

A

Find empirical formula
Add atomic masses in the empirical
Add the Mr for molecule divide by mass of atoms (empirical)
Times the molecule by this

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4
Q

What is redox

A

Reaction where reduction and oxidation take place

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5
Q

How can you tell if a molecule has been reduced/oxidised in a redox reaction

A

By oxidation states, transfer of electrons
Oxidation is an increase in oxidation state - lost electrons
Reduction is a decrease in oxidation state - gain electrons

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6
Q

What is the oxidation number of an uncombined element

A

0

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7
Q

What is the oxidation number of ions

A

What the ion charge is e.g NO3^- would be -1

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8
Q

What is the oxidation number of fluorine

A

Always -1

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9
Q

What is the oxidation number of oxygen

A

In all compounds -2, except peroxides -1 of combined with fluorine +2

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10
Q

What is the oxidation number of hydrogen

A

In all compounds +1 except metal hydrides -1

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11
Q

What is the oxidation number of chlorine

A

-1 except when with oxygen and fluorine, need to work it out

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12
Q

What is the oxidation number of group 1 and 2 metals

A

Group 1 is +1

Group 2 is +2

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13
Q

How do you find the oxidation number of a element in a compound

A 
e.g CO3^-2
O=-2
C + (-2 x3) = -2
C - 6 = -2
C = 14
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14
Q

What is disproportionation

A

Same element in one reaction gets oxidised and reduced

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15
Q

What always occurs at the anode

A

Oxidation

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16
Q

What always occurs at the cathode

A

Reduction

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17
Q

What is the ionic equation for brine electrolysis

A

2Cl^- + 2H2O -> Cl2 + H2 + 2OH^-

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18
Q

What is the half equation of brine electrolysis at the anode

A

2Cl^- (aq) -> Cl2 (g) + 2e^-

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19
Q

What is the half equation of brine electrolysis at the cathode

A

2H^+ (aq) + 2e^- -> H2 (g)

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20
Q

What occurs in molten electrolysis

A

Solid ionic compounds don’t conduct electricity as ions in solid not free move
Ionic compound melted, charged ions in solid not free move, carry current
In molten electrolysis, cathode makes metal and anode makes non-meta, (except hydrogen)

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21
Q

What happens in solution electrolysis

A

Easier than molten
Dissolved ionic compound, ions free can carry current
Water compete with ions from salt

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22
Q

What can be made at the cathode

A

Hydrogen if metal is stronger than hydrogen - group 1/2 or is Al
Metal for all other salts
Hydrogen made on acid electrolysis

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23
Q

What can be made at the anode

A

Halogen if salt is a halide
Oxygen if salt is sulfate/nitrate
Oxygen if hydroxide electrolysis

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24
Q

How do you balance a redox reaction

A
  1. Balance atoms
  2. Balances charges using oxidation states (including moles)
  3. Multiply the opposite charge to opposite atom
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25
Q

How do you nomenclature (name) using oxidation states

A 
Use oxidation states to work out the other element in compound 
e.g Ni(NO3)2 
x1 Ni^2+
x2 NO3^-
O = -2 x 3 = -1
N = -6 = -1 
N = 5
Nickel Nitrate (V)
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26
Q

What are iodine-sodium thiosulfate titrations used for

A

Help find concentration of oxidising agent

More concentrated oxidising agent is, more ions oxidised by certain volume of it

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27
Q

How do you find the concentration of potassium iodate (V) KIO3
IO3^- (aq) + 5I^- (aq) + 6H^+ -> 3I2 (aq) + 3H2O (l)

A

Use oxidising agent to oxidise as much iodide as can, measure certain volume e.g 25cm^3 of KIO3. Add excess KI to solution. Iodate (V) ions in KIO3 solution oxidise some iodide ions to iodine
2. Find amount iodine moles made by titrating (use starch indicator to detect iodine -> black) make sodium thiosulfate
I2 (aq) + 2S2O3^2- (aq) -> 2I ^- (aq) + S4O6^2- (aq)
Iodine fully reacts with 11.1cm^3 of 0.120moldm^-3 thiosulfate
Moles = 0.120x11.1/1000 = 1.332x10^-3mol
3. Oxidising agent concentration (use original equation) = 2.22x10^-4x1000/25.0 = 8.88x10^-3moldm^-3

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28
Q

How can you make a titration accurate

A

Use burette
Do rinsings
Do repeats

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29
Q

What are the problems with iodine-sodium thiosulfate titrations

A

Solutions used react very slow with oxygen in air

If add starch solution too soon, iodine ‘stick’ to it so won’t react, unreliable, only add when pale yellow

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30
Q

What form of compound is a halogen always in

A

Always combined and exist as diatomic molecules e.g Cl2

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31
Q

Why don’t halogens dissolve in water

A

They’re non-polar

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32
Q

Why are all halogens volatile

A

Weak attractive forces between molecules

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33
Q

What occurs to the melting/boiling points down halogens

A

Down group id-id bonds stronger gets bigger so increase down group as molecules larger (more electrons) stronger intermolecular forces

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34
Q

What is fluorine at room temperature

A

Play yellow gas

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35
Q

What is chlorine at room temperature

A

Green gas

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36
Q

What is bromine at room temperature

A

Dark red volatile liquid

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37
Q

What is iodine at room temperature

A

Shiny black solid

Sublime, purple vapour

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38
Q

What are the isotopes and percentage abundances of fluorine

A

19F = 100%

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39
Q

What are the isotopes and percentage abundances of chlorine

A 
35Cl = 75%
37Cl = 25%
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40
Q

What are the isotopes and percentage abundances of bromine

A 
79Br = 50%
81Br = 50%
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41
Q

What are the isotopes and percentage abundances of iodine

A

127I = 100%

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42
Q

How does the water solubility change in the halogens

A

Decreases down the halogens group

43
Q

What are halogens more soluble in

A

Organic solvents

44
Q

What colour is chloride in cyclohexane and water

A

Cyclohexane - pale green

Water - almost colourless

45
Q

What colour is bromide in cyclohexane and water

A

Cyclohexane - red/orange

Water - yellow

46
Q

What colour is iodine in cyclohexane and water

A

Cyclohexane - violet

Water - brown

47
Q

Why are halogens good oxidising agents

A

Halogens tend to remove and election from others to form full outer shell, all oxidising agents

48
Q

Which is the best oxidising agent that’s a halogen

A

Fluorine most reactive and strongest oxidising agent

49
Q

How does oxidising agent change down halogens

A

Down group less effective oxidising agents (worse at gaining electron) greater distance between nucleus and outer shell (atoms bigger), more shielding so electrons less attracted

50
Q

What happens in a halogen-halide redox reaction if add aqueous halogen solution to solution with halide ions

A

Only displace halides if below them on periodic table

Thing displaced is oxidised and thing that does displacing is reduced

51
Q

What is the ionic equation for chlorine water (colourless) and potassium bromide solution (colourless)

A

Cl2 (aq) + 2Br ^- (aq) -> 2Cl^- (aq) + Br2 (aq)

52
Q

What is the ionic equation for bromine water (orange) and potassium iodide solution (colourless)

A

Br2 (aq) + 2I^- (aq) -> 2Br^- (aq) + I2 (aq)

53
Q

What is the ionic equation for chlorine water (colourless) and potassium iodide solution (colourless)

A

Cl2 (aq) + 2I^- (aq) -> 2Cl^- (aq) + I2 (aq)

54
Q

What happens to bromide when displaced

A

Bromine formed, turns orange

55
Q

What happens if iodine is displaced

A

Iodine formed, turns brown

Iodide oxidised 2I^- -> I2 + 2e^-

56
Q

What is formed when halide ions react with silver ions, and general equation

A

Solid precipitate forms
Silver halide insoluble, are precipitated when solution of silver ions added to halide ions solution.
Ag^+ (aq) + X^- (aq) -> AgX(s)

57
Q

What colour precipitate formed from silver chloride, and ionic equation

A

White

Ag^+ (aq) + Cl^- (aq) -> AgCl (s)

58
Q

What colour precipitate formed from silver bromide, and ionic equation

A

Cream

Ag^+ (aq) + Br^- (aq) -> AgBr (s)

59
Q

What colour precipitate formed from silver iodide, and ionic equation

A

Yellow

Ag^+ (aq) + I^- (aq) -> AgI (s)

60
Q

How can you tell the difference between halide ions

A

Add ammonia solution
AgCl - soluble
AgBr - sparingly soluble
AgI - insoluble

61
Q

Which halide ions are decomposed

A

Silver chloride and silver bromide both decomposed by light to make silver metal and halogen
light
e.g silver bromide -> silver + bromide

62
Q

How is a large amount of HCl made as a co-product

A

Co-product of chlorination or organic compounds

63
Q

How can hydrogen chloride be converted to hydrochloric acid

A

Passing through water
High concentration solution can be made easily as hydrogen chloride high water solubility
Hydrogen chloride gas made of covalent molecules - dissolved in water forms hydrated H^+ (aq) and Cl^- (aq)

64
Q

What does sodium fluoride and sodium chloride form when react with concentrated sulfur if acid

A

Make hydrogen fluoride/chloride gas
See white fumes of hydrogen chloride as meets moist air
Tiny hydrochloric axis droplets made

65
Q

What forms when sodium bromide reacts with concentrated sulfuric acid

A

Hydrogen bromide

Bromide ions not strong enough reducing agent to reduce sulfuric acid to sulfur dioxide

66
Q

Why is adding concentrated sulfuric acid to sodium bromide not an efficient way of making hydrogen bromide

A

Not pure is a mix of hydrogen bromide, sulfur dioxide and bromine vapour

67
Q

What forms when sodium iodide reacts with concentrated sulfuric acid

A

Hydrogen iodide

As strong enough reducing agent do sulfuric acid reduces further into hydrogen sulfide gas

68
Q

Why is adding concentrated sulfuric acid to sodium iodide not a good way to make hydrogen iodide gas

A

Not pure, gas made will be mix of hydrogen iodide (white flumes) and hydrogen sulfide

69
Q

How can you make pure hydrogen bromide/iodide

A

Use concentrated phosphoric acid, isn’t reduced, so pure hydrogen halide

70
Q

What happens to the thermal stability down group 7 halogens

A

Down group decreases in thermal stability as down group increase outer shells. Hydrogen fluoride has the strongest covalent bond as shortest bond

71
Q

What happens what hydrogen fluoride is heated

A

Not broken down

72
Q

What happens to hydrogen chloride when heated

A

Not broken down

73
Q

What happens to hydrogen bromide when heated

A

Some brown bromide gas made when strongly heated

74
Q

What happens to hydrogen iodide when heated

A

Lots purple gaseous iodide made if red hit needle plunged into hydrogen iodide

75
Q

Which is the least acidic hydrogen halide

A

All acidic except hydrogen fluoride, not strongly

76
Q

What percentage of dissociation occurs and which hydrogen halides

A

100%

HCl, HBr, HI

77
Q

What ion does all acidic solution contain

A

H^+ (aq) ions, shown as oxonium ion H3O^+ (aq)

HCl + H2O -> H3O^- (aq) + Cl^- (aq)

78
Q

What do hydrogen halides react with to make salts, what is the experiment

A

Ammonia
Glass rod dipped in concentrated ammonia solution placed in hydrogen halide, white cloud given of ammonium halide made
NH3 + HCl -> NH4^+ + Cl^-

79
Q

Why do hydrogen halide reactions differ with concentrated sulfuric acid

A

Increasing strength of halide ions as reducing agents, solid halides with sulfuric acid

80
Q

What forms when hydrogen fluoride/chloride reacts with sulfuric acid

A

No reaction

81
Q

What forms when hydrogen bromide reacts with concentrated sulfuric acid

A

Makes sulfur dioxide

82
Q

What forms when hydrogen iodide reacts with concentrated sulfuric acid

A

Makes hydrogen sulfide

83
Q

What can happen if exposed to chlorine gas in small dose

A

Irritate eyes, skin, respiratory system

84
Q

What happens if inhale chlorine concentrations of 40ppm+

A

Reacts in lungs form hydrochloric acids, affect lung tissue and causes drowning as liquid floods lungs

85
Q

How is chlorine transported if not made at site

A

By road or rail in specially designed pressurised tank containers

86
Q

What may be on a lorry or on the tank carrying chlorine

A

Hazchem warning plate attached to tank when transported incase fire brigade need information

87
Q

How is chlorine transported and what happens if the temperature or pressure gets too high i

A

Liquid as more can be stored than gas under pressure

If too high pressure or temperature tanks have pressure release devices designed to vent tank, realise some gas

88
Q

What are tanks usually lined with, and why must inside the tank be dry

A

Steel

As chlorine reacts with water to produce corrosive acids

89
Q

What happens if there is too much liquid discharge

A

Large chlorine tanks is excess flow valve, designed to close automatically if angle valve which regulates discharge of liquid chlorine at exit port exceeds some predetermined value

90
Q

Why is a scrubber unit used when transferring from rail tanker to bulk trailer on site

A

Scrubber unit ensures air being displaced from bulk trailer has chlorine removed

91
Q

What is on the scrubber that is used to remove chlorine

A

Has sodium hydroxide solution, reacts with chlorine makes sodium chlorate (I) - bleach which is sold on

92
Q

How is chlorine stored and moved

A

In cylinders

Use hoist to move them avoiding damage

93
Q

How do they check stored cylinders

A

Take stick soaked in concentrated ammonia solution over end if leaking white cloud of ammonium chloride seen

94
Q

What are the uses of chlorine

A

Water treatment, kill bacteria and other pathogens, chlorination of water decrease in typhoid
Household bleach products, kills bacteria, remove stains from clothes

95
Q

How does bleach remove stains from clothes

A

Is oxidising agent so removed stains by breaking bonds in coloured chemicals to form colourless products

96
Q

What is equilibrium

A

Reaction can go forward and backward
Rates are equal
Concentration of reactants and products stay same

97
Q

What condition does an equilibrium reaction have to be under and why

A

Closed system so that nothing goes in or out

98
Q

Why aren’t high pressures used

A

Too expensive to obtain and the equipment is expensive

99
Q

What is the equilibrium constant

A

Kc
aA + bB cC + dD
Kc = [products]/[reactants]

100
Q

How does the concentration affect Kc

A

Equilibrium shifts to try keep reactants and products same

Kc unchanged

101
Q

What affects Kc

A

Temperature always

Pressure if it is a gas

102
Q

What is Le Chatelier’s principle

A

If a system (reactant and product chemicals) at equilibrium and change made in any of conditions then the system will oppose change

103
Q

How do catalyst affect equilibrium

A

No effect as only speed up rate of both reactions

Reduces time for equilibrium to be reache d

104
Q

How does pressure affect equilibria

A

The amount of moles on each side

e.g if increasing pressure, shifts equilibrium to side with fewer gas molecules, reduces pressure

Chemistry (5 decks)

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