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iGCSE Revision > Chemistry MOCK > Flashcards

Chemistry MOCK Flashcards

1
Q

What are the states of matter and what determines them?

A

Solids, liquids, and gases. Can be determined by temperature, as it gives particles more energy, or pressure as the particles are closer together … the intermolecular attraction will be made stronger.

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2
Q

Describe the particles of a solid.

A

Particles have strong forces of attraction and are in fixed positions with a regular lattice arrangement. They have a definite shape and volume. The particles vibrate about their positions.

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3
Q

Describe the particles of a gas.

A

Particles have very weak forces of attraction and can move about in straight lines, and are spaced out. They can change volume and will fill any container.

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4
Q

Describe the particles of a liquid.

A

Particles have have weak forces of attraction, are randomly arranged and can move about. They are constantly moving with random motion. Liquids have a definite volume.

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5
Q

Describe particle changes from solid to liquid to gas.

A

When a solid is heated the particles gain energy. They vibrate more, and the attraction weakens. They break free from their positions. When changing to a gas they move faster and break their bonds altogether.

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6
Q

What is diffusion?

A

The gradual movement of particles from high concentrations of that particle to low concentrations of that particle.

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7
Q

How is an atom made up?

A

The nucleus is in the middle with equal numbers of neutrons and protons. The nucleus has a positive charge with all the protons, and also makes up the atomic mass.
The electrons move around the nucleus in shell levels. They are the same number as the neutrons and cancel out the charge.

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8
Q

What is the atomic number and mass number?

A

The atomic number is the number of protons, and the mass number is the number of protons and neutrons. From this you can work out the number of neutrons.

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9
Q

What is the difference between compounds, elements, and mixtures?

A
  • Elements have only one element.
  • Compounds are two or more elements chemically bonded, with different properties (Eg. Iron Sulphide is not magnetic)
  • Mixtures have no chemical bonds and can be easily separated.
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10
Q

How to separate an insoluble solid from a liquid?

A

Use filtration, filter the filtrate and leave behind the residue.

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11
Q

How do you use crystallisation and recrystallisation?

A

Recrystallisation can purify compounds, by putting them in solution, and heating them so the compound dissolves and becomes supersaturated. Let this cool and the solvent evaporates, leaving a purer compound.
Crystallisation is just a way of obtaining a solid from a solution in the same way.

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12
Q

How would you separate rock salt?

A

Grind it up, dissolve the salt in water, filter it to get the sand, then heat the salt water to evaporate the water.

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13
Q

How does chromatography work?

A

The solvent soaks up the paper, and the dies dissolve in it. They then move up the paper with the solute. How far they move depends on how well they dissolve and how much they stick to the paper.

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14
Q

How does simple distillation work and what would you use it for?

A

Used to separate out solutions. Heat the solution in a round bottomed flask and let the solvent evaporate. It will condense in the liebig condenser.

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15
Q

How does fractional distillation work and what would you use it for?

A

Used to separate a mixture of liquids. In the fractionating column liquids evaporate and condense repeatedly until they reach the top and go into the liebig condenser. The liquids with the lowest boiling point will come out first.

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16
Q

What can you say about elements in the same group in the periodic table?

A

They have the same no. of electrons in the outer shell, and as a result have similar properties.

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17
Q

Describe ionic bonding.

A

It happens between a metal and a non metal, where electrons are transferred from one atom to another to give each atom full outer shells. Ions are formed, which are attracted to each other.

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18
Q

What do you call negative and positive ions?

A

Cation +, anion -

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19
Q

What are the characteristics of Giant ionic structures and why?

A

They have high melting points and boiling points as a lot of energy is required to break the bonds.

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20
Q

How does covalent bonding work?

A

Two non metals share some electrons so they both have full outer shells. There is a very strong attraction between the shared electrons and the two nuclei.

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21
Q

What are the formulas for ammonia and methane?

A

NH3 and CH4

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22
Q

What are the characteristics of covalent molecules and giant covalent structures?

A
  • Covalent molecules have weak intermolecular forces and so have low melting points.
  • Giant covalent structures have all the atoms bonded together strongly, which takes a lot of energy to break , and so there are high melting points. They usually don’t conduct electricity and are insoluble in water.
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23
Q

Why is diamond so strong?

A

Each atom has four covalent bonds in a very rigid structure.

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24
Q

What are the characteristics of graphite and why?

A

It is made up of layers that can slide over each other - easy to break. Good conductor of electricity because it contains delocalised electrons.

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25
Q

What are isotopes?

A

They are different atomic forms of the same element that have different numbers of neutrons but the same amount of protons.

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26
Q

How would you work out the relative atomic mass of an element?

A

Multiply the masses of the different isotopes buy their abundance. Then add them together and divide by the abundances put together.

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27
Q

How can you work out the relative formula mass of a compound?

A

Find out the relative formula masses of the different atoms, multiply them by how many of those atoms there are and add everything together.

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28
Q

What is the empirical formula?

A

It is the smallest whole number ratio of atoms in a compound.

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29
Q

How can you work out the empirical formula of a compound used in an experiment?

A

Write down the different masses of the different elements used, and divide them by their relative formula masses to work out roughly how many atoms were used. Then multiply/ divide them to get a whole number.

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30
Q

How can you work out the molecular formula of a compound used in an experiment?

A

Find out the relative formula mass of the compound and then divide the mass used by that. Multiply all the elements in the empirical formula by this.

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31
Q

How can you work out the masses used / made in reactions if you know one already?

A
  • First write out the balanced equation.
  • Find the relative atomic masses of the different ingredients.
  • Multiply/ divide them to get the answer.
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32
Q

How can you work out the number of moles in a substance?

A

Divide the mass of the substance by the molar mass.

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33
Q

What is the structure of a hydrated salt?

A

It is a lattice of positive and negative ions with the water in between.

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34
Q

How can you work out how much water of crystallisation a salt contains.

A
  • First work out the number of moles of salt and the number of moles of water used by dividing masses used by the molar mass.
  • Multiply/ divide these to get a close to whole number ratio.
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35
Q

What are periodic table rows and columns called, and how are whey organised? What is the the top of the staircase?

A

Periods have the same number of electron shells.
Groups have the same no. of electrons in the outer shell.
Al

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36
Q

Which type of oxides are basic and acidic?

A

Metal oxides are basic.

Non-metal oxides are acidic.

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37
Q

Why do alkaline metals get more reactive?

A

The electrons are further away from the nucleus, so the attraction is weaker, and the bonds can break more easily.

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38
Q

Describe what happens when you put different alkaline metals in water.

A

Lithium fizzes on the surface slowly producing lithium hydroxide and hydrogen.
Sodium fizzes rapidly around the surface producing sodium hydroxide and hydrogen.
Potassium reacts vigorously and burns with a lilac flame, producing potassium hydroxide and hydrogen.

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39
Q

What are the colours and physical states of the halogens?

A

Chlorine is a green gas.
Bromine is a red-brown liquid.
Iodine is a grey solid.

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40
Q

What does hydrogen chloride gas do in water?

A

It dissociates to produce H+ ions and Cl- ions, making hydrochloric acid.

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41
Q

What is a displacement reaction?

A

When a more reactive element displaces a less reactive element from a compound.

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42
Q

What is the loss/gain of electrons?

A

Oxidation is loss, reduction is gain.

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43
Q

What do you call the elements that swap in a displacement reaction?

A

An oxidising agent accepts electrons and gets reduced.
A reducing agent gives electrons and gets oxidised.
When this happens at the same time it is a redox.

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44
Q

What happens when an acid reacts with a metal?

A

It produces a metal salt and hydrogen.

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45
Q

What happens when a metal reacts with water (or steam)?

A

It will give a metal hydroxide and hydrogen.

46
Q

What is the first ten in the reactivity series?

A

Potassium, Sodium, Lithium, Calcium.
Magnesium, Aluminium, Zinc.
Iron, Copper.
Silver, Gold.

47
Q

What causes rust and what is the word equation?

A

When iron or it alloys are exposed to oxygen and water and it oxidises.
iron + oxygen + water goes to hydrated iron(III) oxide

48
Q

What are two ways to prevent rusting?

A
  • Barrier methods such as painting or coating with plastic, or oiling or greasing for moving parts.
  • Using a sacrificial method using a more reactive metal such as zinc to react with the water and oxygen. This can be in the form of an anode or galvanised (coated).
49
Q

What are the proportions of the three most common gases in the atmosphere?

A

78% nitrogen
21% oxygen
1% argon

50
Q

What is an experiment using copper to show the percentage of oxygen in the air?
What is the equation?

A
  • Place some excess copper in a glass tube that is connected to two syringes.
  • Heat the copper and note the difference in volume of the gas in the syringes from the start.
  • 2Cu + O2 goes to 2CuO
51
Q

What is an experiment using iron to show the percentage of oxygen in the air?

A
  • Soak some iron wool in acetic acid to catalyse the experiment.
  • Put the wool in a test tube and invert it in some water.. Mark the water level.
  • Mark how high the water has risen and find the difference in volumes.
52
Q

How can you make O2 in the lab?

A
  • Decompose some hydrogen peroxide (H2O2)
  • Use manganese(IV) oxide as a catalyst.
  • 2H2O2(aq) goes to 2H2O + O2
53
Q

What happens when you burn magnesium, carbon, or sulfur in air?

A
  • Magnesium burns with a bright white flame to form a white powder, magnesium oxide (MgO). This is a base.
  • Carbon will burn with a yellow flame to form carbon dioxide. This is slightly acidic in water.
  • Sulfur will burn with a pale blue flame and forms sulfur dioxide (SO2). This is acidic in water.
54
Q

What gases would you use upward delivery?

A

Gases less dense than air, for example H2.

55
Q

What gases would you use a downward delivery?

A

Gases more dense than air, for example CO2 and Cl2

56
Q

How can you make carbon dioxide from marble?

What is the equation?

A
  • Put some marble chips in some hydrochloric acid.

- 2HCl + CaCO3 goes to CaCl2 + H2O + CO2

57
Q

How can you make carbon dioxide by thermal decomposition?

A
  • Heat a metal carbonate so it breaks down into a metal oxide and carbon dioxide.
58
Q

How does Carbon dioxide create global warming?

A
  • It is a greenhouse gas that greats an insulating layer in the atmosphere that absorbs heat that would normally be radiated out into space.
59
Q

What metal ions can you identify with flame tests?

A
  • Lithium + ions burn with a red flame
  • Sodium + ions burn with a yellow flame
  • Potassium + ions burn with a lilac flame
  • Calcium 2+ ions burn with a orange red flame.
60
Q

What metals give coloured precipitate compounds, and what in?

A

Cu 2+ ions form Copper(II) hydroxide Cu(OH)2 precipitate in NaOH, which is blue.
Fe 2+ ions form Iron (II) hydroxide Fe(OH)2 precipitate in NaOH, which is green.
Iron 3+ ions form Iron(III) hydroxide Fe(OH)3 precipitate in NaOH, which is brown.

61
Q

What is the formula for and how can you test for ammonia gas?

A

NH3 can be tested for with damp red litmus paper. It should turn blue.

62
Q

How would you test for carbonates?

A

Mix with HCl and check if it gives off CO2.

63
Q

How would you test for sulphates?

A

Add some HCl to acidify, and they add barium chloride solution, BaCl2 (2+). This reacts with the Sulfate ions SO4 (2-) to form BaSO4, which is a white ppt.

64
Q

How would you test for three of the halides?

A

Acidify with some Nitric acid (HNO3) to remove carbonate or sulphide ions, and then add some silver nitrate solution (AgNO3).

  • Cl- gives a white ppt of silver chloride.
  • Br- gives a cream ppt of silver bromide.
  • I- gives a yellow ppt of silver iodide.
65
Q

How would you test for Chlorine, Oxygen, Carbon dioxide, and hydrogen?

A
  • Bleaches damp litmus paper white.
  • Relights a glowing splint.
  • Turns limewater cloudy.
  • Combusts with a “pop” off a lighted splint.
66
Q

What are the differences between hydrous and anhydrous Copper(II) sulphate?

A
  • Hydrous is blue

- Anhydrous is white.

67
Q

What is a physical test for different elements?

A

Boiling and melting points can be tested to check if a substance is pure.

68
Q

What are two other indicators to universal indicator?

A

Phenolphalein is colourless in acids and pink in alkalines.

Methyl orange is red in acids and yellow in alkalines.

69
Q

What is an acid and what is an alkaline? What happens when you mix them together

A
  • An acid is a source of H+ ions.
  • An alkaline is a source of OH- ions.
  • They neutralise to form water.
70
Q

What happens when a metal oxide reacts with acid?

A

It forms salt and water

71
Q

What happens when a metal carbonate reacts with an acid?

A

It forms salt, water, and carbon dioxide.

72
Q

How would you test for ammonia?

A

It turns damp red litmus paper blue.

73
Q

What types of salts are soluble and what are the exceptions?

A
  • Sodium, potassium, and ammonium.
  • Chlorides except silver.
  • Sulphates except barium and calcium.
74
Q

What factors does the rate of reaction depend on?

A

Temperature,
Concentration,
Catalyst,
Size of Particles.

75
Q

How do you work out the rate of reactions?

A

Amount of reactant used or product formed / time.

76
Q

What are three ways to measure the rate of reaction?

A
  • Watch for how long it takes for a precipitate formed to obscure a marker.
  • Measure the change in mass as a gas is given off.
  • Measure the volume of gas given off with a gas syringe.
77
Q

How can you investigate the rate of reaction with marble chips?

A

Put them in hydrochloric acid, and measure the mass or volume. Try this with different sized chips.

78
Q

What is the formula for sulphuric and nitric acid?

A

H2SO4 and HNO3.

79
Q

What are the four types of iron and their uses?

A
  • Wrought iron (pure) is for gates/railings.
  • Cast iron is used for cooking pans.
  • Steel is strong and make for car bodies.
  • Stainless steel is for cutlery.
80
Q

How can you calculate the heat energy transferred? What are the units?

A

mass of water x temperature change x specific heat capacity (4.2). The answer is in joules.

81
Q

What are hydrocarbons? What are the first five?

A

They are molecules made of H and C only. They are long chains.
Methane, Ethane, Propane, Butane, Pentane.
(mice eat pink buns)

82
Q

How do you know how many atoms are in a hydrocarbon?

A

however many carbon atoms, plus twice as many hydrogen and two H on either end.

83
Q

What is the difference between complete and incomplete combustion?
What is the equation for the combustion of a hydrocarbon?

A

Complete combustion happens when there is plenty of oxygen, and it burns with a clean blue flame.
Incomplete combustion happens when there is not enough oxygen, and a smokey flame.
Ch4 + 2O2 goes to CO2 + 2H2O

84
Q

What is an alkene? What are names for some, and what are the structures like?

A

It is a hydrocarbon that has a double bond between two of the carbon atoms, e.g.. Ethene, propene…etc. They are unsaturated because more atoms can join on to them. They can have the same formulas, but different structures which are called isomers.

85
Q

What can alkenes react with?

A

They can react with halogens to form haloalkanes. The double bond on the alkene splits, and the halogens are added to the ends.

86
Q

What is a test for alkenes?

A

Mix it with orange bromide water, and see if it becomes colourless. The bromine reacts with the alkene to form a dibromoalkane.

87
Q

How can you find out how much acid is needed to neutralise an alkali (or vice versa)?

A

Use a titration:

  • Using a pipette, fill a conical flask with some alkali/acid.
  • Add some drops of phenolphthalein.
  • Use a burette to measure the alkali/acid you add to the alkali/acid.
  • Swirl it, and see when it changes colour.
  • Which one you add to which depends on the question.
88
Q

How do you work out concentration?

A

Number of moles / volume (dm^3)

89
Q

What are the raw materials used in extracting iron? Why are they used?

A
  • Iron ore, hematite, Fe2O3, is the source of iron.
  • Coke, carbon, reduces the iron oxide to iron metal.
  • Limestone takes away the impurities in the form of slag.
90
Q

What four things affect the rate of reaction and how?

A
  • Higher temperature means faster particles and more frequent and energetic collisions.
  • Greater concentration means there are more particles present, so they collide more frequently.
  • Larger surface area means that there is a greater number of exposed particles to react, meaning that there are more collisions.
  • A catalyst lowers the activation energy by providing an alternate route.
91
Q

How can you measure the rate of reaction with marble chips?

A

Use a known volume of HCl, and a known mass of cable chips in a conical flask to react. Measure the CO2 given off at intervals with a gas syringe.

92
Q

How can you measure the rate of reaction with magnesium metal?

A

Add a known mass of magnesium to a known volume of HCl in a conical flask, and stand it on a balance. Measure the mass loss of the whole apparatus at intervals.
Mg + 2HCl goes to MgCl2 + H2

93
Q

How can you measure the rate of reaction with hydrogen peroxide?

A

Put the H2O2 in a flask with manganese (IV) oxide catalyst, and measure the O2 gas given off in a syringe at intervals as it decomposes.

94
Q

What are the differences between endothermic and exothermic reactions?

A

Endothermic reactions take energy in from the surroundings, and bonds are broken. This means that there is a positive enthalpy change (/\H +)
In exothermic reactions, bonds are formed and energy is released. This means that there is a negative enthalpy change (/\H -)

95
Q

What do energy level diagrams look like?

A

The y axis is the energy, and x is the progress of the reaction.
The reactants start at a particular energy level, activation energy is added, and the products end up at another level.

96
Q

How does adding a catalyst change a energy level diagram?

A

It lowers the activation energy, so the curve is lower, but the overall energy change, as well as starting and ending points remain the same.
Catalysts are unchanged by the reaction.

97
Q

What is meant by “activation energy”?

A

It is the minimum amount of energy required for a reaction to occur.

98
Q

How can you measure the enthalpy change of a displacement or neutralisation reaction?

A

Measure the temperature of the reactants, making sure that they are the same. Put them in a polystyrene cup with insulation around. Measure the temperature at the end of the reaction.

99
Q

How can you find out the enthalpy change of a combustion reaction?

A
  • Burn a known mass of fuel underneath a beaker of water, and record the change in temperature. Measure the change in mass of the fuel to see how much was burnt.
  • Make sure you protect the experiment from draughts.
100
Q

What is a reversible reaction, and what are two examples of some?

A
  • It’s a reaction where the products can react to turn back into the reactants. It is shown by the double arrow.
  • The dehydration of copper (II) sulphate CuSO4
  • Heating ammonium chloride will produce ammonia gas and HCl gas. Cooling it back down will produce ammonium chloride (NH4Cl)
101
Q

Describe an experiment for diffusion with bromine gas.

A

Bromine gas is brown and air is clear, so if you join two jars of the stuff together you can see the brown colour slowly fill the whole container.

102
Q

Describe an experiment for diffusion in a glass tube.

A

Ammonia gas and hydrogen chloride gas (both come from their aqueous version), can be soaked into cotton wool. Place both buds at different ends of the sealed tube and watch a white ring of ammonium chloride appear near the HCl. The ammonia gas is lighter and moves faster.

103
Q

How is crude oil separated?

A

They use fractional distillation, where the oil is heated so most of it turns into a gas. They enter near the bottom of the fractionating column. The column is hottest at the bottom, and gets colder so the different fractions condense at different levels.

104
Q

What are the different fractions in crude oil, and what are some uses?

A

Great Gorillas Not Knowing the Diesel Oil Business:

  • Gases, for glass manufacture
  • Gasoline for cars
  • Naphtha to make plastics
  • Kerosene for jet fuel
  • Diesel for diesel engines
  • Fuel Oil for central heating
  • Bitumen for making roads surfaces.
105
Q

What happens during incomplete combustion?

A

Carbon monoxide is formed when hydrocarbon fuels are burnt without enough oxygen. This is poisonous.

106
Q

What pollutants are formed when you burn fuel?

A
  • Sulfur dioxide is formed form sulphur impurities in the fossil fuels.
  • Nitrogen oxides are created when the temp is high enough for N and O to react to form NO or NO2.
107
Q

What causes acid rain?

A
  • When sulphur dioxide mixes with the clouds to form sulphuric acid H2SO4.
  • When CO2 mixes with the clouds to form carbonic acid.
  • When nitrogen oxides mix with the clouds to form nitric acid HNO3.
108
Q

What are the differences between short and long chain hydrocarbons?

A
  • Short chains have low boiling points because there is less intermolecular attraction. They are thinner and paler. They make better fuels.
  • Long chains have high boiling points because there is a lot of intermolecular attraction. They are more viscous.
109
Q

What happens during the cracking process?

A
  • Long chain hydrocarbons get vaporised and passed over a powdered catalyst at about 600-700 degrees C.
  • Silica (SiO2) and alumina (Al2O3) are catalysts.
  • Shorter chain alkanes and some alkenes are created.
110
Q

What are these? H2SO4 and HNO3

A

sulphuric acid and nitric acid

111
Q

Why are metals malleable?

A

Because the layers of ions can slide over each other, maintaining the bond with the delocalised sea of electrons.

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