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C6 Flashcards

0
Q

What happens to a reaction if reduction takes place?

A

reduction is the gain of electrons

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1
Q

What happens in a reaction if something is oxidised?

A

Oxidation is the loss of electrons

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2
Q

What does redox mean?

A

It means that whenever reduction occurs so must oxidation.

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3
Q

What is the substance that causes something to be oxidised called?

A

An oxidising agent.

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4
Q

Whenever an oxidising agent occurs what happens to it?

A

It is reduced - redox

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5
Q

What is electrolysis?

A

It is the breaking up of a substance using electricity.

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6
Q

What is the substance in electrolysis called and what does it have to be made of?

A

Electrolyte, has to be liquid or liquid dissolved in water

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7
Q

Why can a solid not be an electrolyte?

A

Because the ions must be free moving, which is the case in liquids, but in solids the ions are in fixed positions and can not move.

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8
Q

In electrolysis where is the electricity supplied through?

A

The electrodes

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9
Q

Give an example of an electrode?

A

Carbon rods

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10
Q

In electrolysis what is the positive terminal called?

A

Anode

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11
Q

In electrolysis what is the negative terminal called? I

A

Cathode

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12
Q

What current must the electricity have?

A

DC direct current

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13
Q

In electrolysis which ions move to which electrode? And why?

A

Positive ions = cathode
Negative ions = anode
Because ions move to the oppositely charged electrode.

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14
Q

What happens to the negative ions at the anode?

A

The ions loose extra electrons to become neutral.

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15
Q

In electrolysis what happens to the positive ions at the cathode?

A

The ions gain enough electrons to neutralise their positive charge so that they become neutral.

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16
Q

What is different about the electrolysis of aqueous solutions?

A

Ions from the water are also present eg. Hydrogen and hydroxide ions

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17
Q

In the electrolysis of aqueous solutions what is the rule for what happens at the anode?

A

If a halogen is available it will be formed, but if not the. The hydroxide ion breaks down to release oxygen.

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18
Q

In the electrolysis of aqueous solutions what is the rule for which ion goes to the cathode?

A

The reactivity series tells you, the least reactive substance is discharged and ions that aren’t discharged remain in the solution.

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19
Q

Does the solution in electrolysis have to be molten?

A

No, it can be aqueous

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20
Q

Describe the electrolysis of copper chloride.

A

An electrical current is sent through the electrolyte which causes it to decompose. This starts a flow of charge through the electrolyte. The negative chloride ions attract to the anode and form chlorine gas, the positive copper ions attract to the cathode to form pure copper.

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21
Q

What are the half equations for the electrolysis of CuSO4?

A

Anode: _ _
4OH === O2 + 2H2O + 4e
cathode: 2+ _
Cu + 2e ==== Cu

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22
Q

At which electrode in electrolysis is the metal always formed?

A

Cathode - except for Hydrogen

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23
Q

What is the oxidation number of any pure element?

A

0

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24
What is the oxidation number of hydrogen when it is in a compound without a metal?
+1, with a metal -1
25
What is the oxidation number of O in a compound? Or with H2 or Na2
-2, -1
26
What is the oxidation number of alkali metals in compounds?
+1
27
What is a fuel cell?
An electrical cell that is supplied with a fuel and oxygen, and uses energy from the reaction to produce electricity.
28
Give an example of a fuel cell?
Hydrogen-oxygen fuel cell.
29
What type of reaction takes place in a fuel cell and why?
Exothermic, because it takes in energy to break bonds and gives out energy to make new bonds.
30
What does a hydrogen fuel cell produce?
It uses hydrogen and oxygen to produce water.
31
Describe how a hydrogen-oxygen fuel cell works in terms of a redox reaction?
The H2 attracts to the anode and the O2 attracts to the cathode. At the cathode O2 gains electrons and reacts with water to make OH- ions. This is reduction. The OH- ions in the electrolyte move to the anode and combine with the hydroxide ions to produce H2O + electrons. This oxidation. Electrons then flow through a circuit from anode to cathode which creates an electrical current.
32
What is the half equation for a hydrogen-oxygen fuel cell at the cathode?
O2 + 4e- + 2H2O ==== 4OH-
33
What is the half equation for the hydrogen-oxygen fuel cell at the anode?
2H2 + 4OH- ===== 4H2O + 4e-
34
Give 3 advantages of using fuel cells.
More efficient then power stations. No pollution, only product is water. Electricity is generated directly from reaction.
35
Give 2 disadvantages to the use of fuel cells.
Producing H2 uses a lot of energy which could cause pollution. Often contain poisonous catalysts which will eventually have to be disposed of, time money and environmental issues.
36
Why are hydrogen-oxygen fuel cells used in spacecrafts?
Lightweight and compact, won't use up valuable room. No moving parts which might go wrong Some product can be used as drinking water. No waste product to get rid of.
37
Why is the car industry interested in fuel cells?
Don't produce conventional pollutants. Hydrogen can be obtained by decomposing water which is largely available meaning we won't have to use non-renewable fuels.
38
What will cause iron to rust?
Both oxygen and water
39
What is the word equation for the rusting of iron?
Iron + water + oxygen ===== hydrated iron(III)oxide
40
Why is the rusting if iron a redox equation?
Iron looses 3 electrons when it reacts with water. This is oxidation. Oxygen gains 2 electrons when it reacts with iron. This is reduction.
41
Name a way that can stop iron from rusting.
By coating the iron with a barrier eg. Paint. Which will keep the water and oxygen out and prevent it from rusting. Oiling/greasing can be used for moving parts.
42
What is tin playing?
Tin plating is where a coat of tin is applied to an object to act as a barrier, stopping water and oxygen from reacting with the surface of iron.
43
What is a disadvantage of tin plating?
If the tin is scratched to reveal iron, the iron will loose electrons and rust even faster.
44
What is galvanising?
Galvanising is where a coat of zinc is put into an object and acts as a sacrificial protection.
45
Why does galvanising iron prevent it from rusting?
It's more reactive than iron so it will loose electrons in preference to iron. It also acts as a barrier blocking out water and oxygen.
46
What do CFCs stand for?
Chlorofluorocarbons
47
What first impression did scientists have about CFCs?
Initially enthusiastic because of their useful properties.
48
What are CFCs useful properties?
Chemically inert - they won't react with other substances Non-flammable Low boiling point Insoluble in water
49
By 1970 how did scientists view CFCs now?
They had gathered evidence that CFCs were responsible for ozone depletion.
50
What does the ozone layer do?
Absorbs and traps UV emitted from the sun preventing most from reaching the earths surface.
51
How do CFCs interfere with the ozone layer?
They interfere with the process of the ozone being broken down and reformed by UV. They cause molecules to break down at a faster rate than they can be reformed.
52
Why is having a hole in the ozone layer bad?
More UV light could reach the earths surface causing an increase in sunburn, ageing of skin, skin cancers and cataracts.
53
What have been used to replace CFCs? And why?
Alkanes - hydrocarbons HFCs Because they don't damage the ozone layer
54
What in CFCs damages the ozone? And why?
Freon - 12 When it enters the atmosphere UV causes freon - 12 bonds to break leaving a chlorine with an unpaired electron - a radical. These radicals female the ozone layer.
55
Show the freon - 12 reacting with UV in terms of equations.
CF2Cl2 ==== Cl• + CF2Cl• Cl• + O3 === ClO• + O• ClO• + O• === Cl• + O2
56
What are chlorine radicals? What does this mean?
Regenerated, 1 chlorine radical can destroy many ozone molecules.
57
Why do scientists now realise that CFCs being inert is a bad thing?
Because it means they stay in the atmosphere for a very long time and will do a lot of damage.
58
What is hard water?
Water which contains high concentrations of magnesium ions and calcium ions.
59
Where is hard water formed?
Formed in areas where natural water flows over rocks which contain calcium and magnesium compounds.
60
What do the rocks that hard water contain which cause hard water? And why does it cause hard water?
Calcium carbonate, which is insoluble, reacts with CO2 and H2O and forms soluble calcium hydrogen carbonate, which is then carried through water and later collected in resviours.
61
What is a disadvantage to hard water?
It makes soap ineffective, doesn't allow soap to form a larger easily which is needed to wash away grease and dirt in the water.
62
How does hard water interfere with soap?
Mg2+ and Ca2+ interfere with this process by reacting with soap to form a deposit of scum. This is a precipitation reaction.
63
How can you get soap to Lather in hard water?
Add more soap - which will cost more
64
How can you test how hard water is?
You can see how soap you need before it begins to lather. The more soap you need the harder the water.
65
What is temp hardness caused by?
Caused by calcium carbonate ions in calcium hydrogen carbonate.
66
What is permanent hardness caused by?
Caused by dissolved calcium sulphate.
67
How can only temp hardness be removed?
By boiling it - calcium hydrogen carbonate decomposes to form insoluble CaCO3.
68
How can both types of water hardness be removed?
By adding sodium carbonate - carbonate ions join into the Ca2+ ions to form an insoluble precipitate of CaCO3.
69
What do all alcohols have in common?
They all have an oxygen atom bonded to a hydrogen atom.
70
In alcohols, how-many bonds does each element have: Carbon, oxygen and hydrogen?
``` Carbon = 4 bonds Hydrogen = 1 bond Oxygen = 2 bonds ```
71
Name the 5 main types of alcohol and their formula in order.
``` Methanol - CH3OH Ethanol - C2H5OH Propanol - C3H7OH Butanol - C3H9OH Pentanol - C4H11OH ```
72
What is fermentation?
It is the process used to convert sugars like glucose into ethanol.
73
How is fermentation brought about?
Through enzymes in the yeast which act as biological catalysts.
74
Why does the temperature in fermentation have to be controlled?
Because if it's too cold the enzymes will be inactive - slow reaction. If it's too hot the enzymes will denature.
75
Why do you have to prevent oxygen getting to the alcohol in fermentation?
Oxygen converts ethanol into ethanoic acid.
76
In fermentation how do you get pure ethanol?
By using fractional distillation after the reaction has stopped.
77
What is the process of hydrating?
Hydrating is the industrial method for producing ethanol. It's when Ethene reacts with steam to make ethanol.
78
In the process of hydrating what is the optimum temp and pressure?
``` Temp = 300 degrees Pressure = 70 atmospheres ```
79
What is the catalyst in the method of hydrating?
Steam heated over a heated phosphoric acid.
80
In terms of manufacture what is the hydrating and fermentation processes like?
``` F = batch process which is slow and inefficient. H = continuous process which is quicker but more expensive. ```
81
In terms of sustainability what is the hydrating and fermentation processes like?
``` F = renewable fuel because it is made from renewable resources. H = non- renewable because it's made from crude oil which will eventually run out. ```
82
In terms of purity what is the hydrating and fermentation processes like?
``` F = has to be distilled before use - not very pure. H = higher purity than fermentation ```
83
In terms of atom economy what is the hydrating and fermentation processes like?
``` F = lower than hydration as not all reactants are used to make ethanol. H = higher than fermentations ```
84
Give 3 examples of animal fats and oils
Lard Blubber Cod liver oil
85
Give 3 exams of vegetable fats and oils
Walnut oil Coconut oil Olive oil
86
What are fats and oils and how are they produced?
They are esters which are produced when glycerol reacts with fatty acids.
87
Why don't oils mix in water?
They are immiscible.
88
How can you mix water and oil to make an emulsion.
To make an emulsion you shake the two vigorously together, breaking up the oil into small droplets which will disperse through the water.
89
Give an example of an emulsion of oil in water.
Milk
90
Give an example of an emulsion for water in oil.
Butter
91
How do vegetable oils get made into soap?
Natural fats are boiled with sodium hydroxide which splits up the fats and oils into soap and glycerol. This is called saponification.
92
What do oils and fats have long molecules of?
Carbon atoms
93
What kind of covalent bonds do saturated and unsaturated oils and fats have between carbons?
``` Saturated = a single covalent bond Unsaturated = at least one double covalent bond. ```
94
What is the name of the unsaturated fat that only has one double covalent bond between carbon?
A monounsaturated fat
95
What is the name of the unsaturated fat that has more than one double covalent bond between carbon?
Polyunsaturated fats
96
How can you test whether an oil or fat is unsaturated or saturated?
You add bromine or bromine water to it, it stays orange it's saturated and if it goes courses it's unsaturated.
97
What can natural unsaturated oils do?
Reduce the amount of blood cholesterol.

Science - C6 (1 decks)

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