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C3 Flashcards

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1
Q

How were elements classified in the 1800s?

A

They were arranged according to their physical and chemical properties and thir relative atomic mass

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2
Q

Give two reasons why Newlands’ Octaves were criticised.

A
  • The groups of elements did not all have similar properties

- He mixed metals and non-metals

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3
Q

How did Newland arrange the elements?

A
  • He noticed that every 8th element had similar properties and listed them in rows of seven. However the pattern broke down when it got to the third row.
  • Presented his work to the Chemical Society in 1865 but his work was criticised.
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4
Q

When did Dmitri Mendeleev arrange the known elements in his Table Of Elements?

A

1869

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5
Q

How did Mendeleev arrange the elements?

A
  • Put elements in order of atomic mass and found he had to leave gaps.
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6
Q

Why did Mendeleev leave gaps in his Table of Elements?

A

In order to keep similar properties in the same columns (now known as groups)

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7
Q

What did the gaps in Mendeleev’s Table of Elements predict?

A

The properties of the then undiscovered elements

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8
Q

How are the group number and the number of electrons in the outer shell related?

A

The group number equals the amount of electrons in the outer shell.
e.g. An element in group 6 will have 6 electrons in its outer shell

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9
Q

How are elements now arranged in the Modern Periodic Table?

A

Arranged by the electronic structure of the elements

-It can predict element’s chemical properties by electron arrangement

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10
Q

What does the positive charge of the nucleus do?

A

Attracts and holds negative electrons in place

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11
Q

What happens if the electrons are further away from the nucleus?

A

The forces of attraction between the nucleus and the electrons of that element are weaker. This causes the element to be more reactive because they can lose the outer shell of electrons easier.

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12
Q

What is shielding?

A

The forces of attraction on the electrons on the outer shell will become weaker, if the atom is bigger, because the inner electrons get in the way of the nucleus’ positive charge. This also causes the element to be more reactive because they are able to lose electron in the outer shell easily.

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13
Q

Name the type of bonds that Group 1 elements form.

A

Ionic bonds. They form ionic compounds with non-metals

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14
Q

What happens as you go down the elements in Group 1?

A
  1. They become more reactive because electrons in the outer shell are more easily lost
  2. They have lower melting and boiling points
  3. Lower density- the first three have a lower density than water which is why they float on top when reacted with H2O.
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15
Q

What are Group 1 elements also known as?

A

Alkali Metals

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16
Q

How many electrons do alkali metals have in their outer shell? What does this do to the properties of the elements?

A
  1. They only have one electron in the outer shell
  2. This makes them very reactive
  3. It also gives them very similar properties
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17
Q

Name the first three alkali metals.

A
  1. Lithium
  2. Sodium
  3. Potassium
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18
Q

Why do alkali metals form ionic compounds with non-metals?

A

They only have one electron in the outer shell so they will lose it to become positive ions. This means they will always form ionic bonds because it is easier to lose one than try and gain or share electrons.
- They produce white compounds that dissolve in water to form colourless solutions

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19
Q

What product is made when an alkali metal reacts with water?

A

Hydrogen gas

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20
Q

What happens when lithium, sodium or potassium reacts with water?

A
  • They float on top of water
  • They fizz furiously
  • They produce hydrogen- (potassium gets hot enough to ignite it)
  • The produce hydroxides that dissolve in water to give alkaline solutions
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21
Q

Give the balanced symbol equation for the reaction between sodium and water.

A

2 Na + 2 H2O ——> 2 NaOH + H2

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22
Q

What are the elements in Group 7 also known as?

A

The Halogens

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23
Q

Explain why Group 7 elements get less reactive as you go down the group from fluorine to iodine.

A

Fluorine has less electrons in the whole atom than chlorine, bromine and iodine. Therefore, it is a smaller element than the others so it gains electrons more easily than the other elements. Iodine, on the other hand, has more electrons in the atom so it has more shells. This makes the electron bigger and further away from the nucleus so the forces of attraction are weaker. This means that it will find it harder to gain electrons and so it is less reactive.

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24
Q

What coloured vapour do the halogens release?

A
  1. Fluorine: very reactive, poisonous yellow gas
  2. Chlorine: fairly reactive, poisonous, dense green gas
  3. Bromine: dense, poisonous, red-brown volatile liquid
  4. Iodine: dark grey crystalline solid or purple vapour
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25
Q

What type of bonds do halogens form with metals?

A

Ionic bonds

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26
Q

What happens in a displacement reaction with halogens?

A

A more reactive halogen will displace a less reactive halogen from an aqueous solution of salt.

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27
Q

Describe the the chemical properties of a typical transition metal.

A
  1. Good conductors of electricity and heat
  2. More dense, strong and shiny than Group 1 metals
  3. Much less reactive than Group 1 metals
  4. Have higher melting points (except mercury-liquid at room temp.)
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28
Q

Give an industrial use for transition metals.

A

Iron catalyst is used in the Haber process
(Manganese(IV) oxide- good catalysts for the decomposition of hydrogen peroxide)
(Nickel useful for turning oils into fats for making margarine)

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29
Q

What are the main ions that cause water hardness?

A

Calcium and magnesium ions

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30
Q

What type of water causes scum and scale?

A

Hard water

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31
Q

What causes temporary hardness?

A

Hydrogencarbonate ion

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32
Q

What causes permanent hardness?

A

Dissolved calcium sulfate

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33
Q

How is temporary hardness removed?

A
  1. By boiling
  2. Softened by adding washing soda
  3. Removed by running water through ion exchange column
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34
Q

How is permanent hardness removed?

A
  1. Softened by adding washing soda

2. Removed by running water through an ion exchange column

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35
Q

How does an ion exchange column remove the hardness of water?

A
  • The columns has lots of sodium ions in it

- The column exchanges them for the calcium and magnesium ions in the water as it runs through the column

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36
Q

How does adding washing soda soften water?

A
  • The added carbonate ions react with the calcium and magnesium ions present in the water already
  • The calcium and magnesium ions are no longer dissolved so they cannot make the water hard
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37
Q

What are the positives of hard water?

A
  • The calcium ions are good for healthy bones and teeth

- People who drink hard water are less likely to develop heart disease

38
Q

How does hard water from scale?

A

When it it is heated it forms scale so the inside of kettles, pipes and boilers are most likely to have scale on

39
Q

How does hard water form scum?

A

When the dissolved calcium and magnesium ions in the water react with soap.

40
Q

During water treatment, how are microbes killed so that the water is safe to drink?

A
  1. The water passes through a mesh screen to remove big bits like twigs
  2. Chemicals are then added to form solids. The solids and microbes stick together and fall to the bottom
  3. The water is filtered through gravel beds to remove all of the solids
  4. The water is then chlorinated to kill off any remaining microbes
41
Q

Explain why tap water is not purified by distillation.

A

The process is too expensive to produce tap water on such a large scale.

42
Q

What is the process of distillation?

A

Boiling water to make steam and then condensing the steam into water, which will now be pure

43
Q

How can people remove substances from their tap water?

A
  • They can buy filters that contain carbon or silver
  • Carbon in the filter removes the chlorine taste
  • The silver is supposed to kill bugs
  • Some people in hard water areas buy water softeners which contain ion exchange resins
44
Q

Why is fluorine added to water in some areas?

A

It helps reduce tooth decay

45
Q

Why is chlorine added to drinking water?

A

To help prevent disease

46
Q

What are the disadvantages of adding chlorine and fluorine to drinking water?

A
  • some studies have linked chlorine in water with an increase to certain types of cancers
  • high doses of fluorine can cause cancer and bone problems
  • Ethics: there is also a concern about whether it is right to mass medicate people as they should be able to choose whether to have fluoride and chlorine in their water
47
Q

What is a reversible reaction?

A

Is a reaction where the products of the reaction can react to produce the original reactants

48
Q

Explain what is meant by an equilibrium.

A
  • If a reversible reaction takes place in a closed system then a state of equilibrium will be reached
  • It means that the amount of reactants and products will reach a certain balance and stay there
  • Reactions are still taking place in both directions but the overall effect is nothing because the forward and reverse reactions cancel each other out.
  • The reactions are taking place at exactly the same rate in both directions
49
Q

How does changing the temperature of a reversible reaction alter the equilibrium position?

A
  • Raising temperature will cause the endothermic reaction to increase to use up the extra heat
  • Reducing temperature will cause the exothermic reaction to increase to give out more heat
50
Q

How does changing the pressure of reversible reaction alter the equilibrium position?

A
  • Raising pressure will encourage the reaction which produces less volume
  • Reducing pressure will encourage the reaction which produces more volume
51
Q

Does adding a catalyst to a reversible reaction change the equilibrium position? Explain your answer.

A

No, because the catalyst will speed up both the forward and reverse reactions by the same amount so it will only make the reaction reach equilibrium quicker.

52
Q

What is the Haber process used for?

A

It produces ammonia, which is used to make fertilisers

53
Q

What are the industrial conditions needed to make ammonia in the Haber process?

A 
Pressure = 200 atmospheres
Temperature = 450 degrees Celsius
Catalyst = Iron
54
Q

Why is the pressure set so high in the Haber process?

A

High pressure favours the forward reaction so the pressure is set high to give the best percentage yield without making the plant too expensive.

55
Q

Why is the temperature 450 degrees Celsius in the Haber process?

A

The forward reaction in the Haber process is exothermic so increasing the temperature will move the equilibrium the wrong way and the yield of ammonia would be smaller. However, lower temperatures would make the rate of reaction much slower so 450C is a compromise between maximum yield and speed of reaction.

56
Q

What to gasses are used during the Haber process to make ammonia?

A

Nitrogen and Hydrogen

57
Q

What kind of reaction is the Haber process?

A

Reversible reaction

58
Q

How is ammonia removed from the reaction vessel? What happens to the left over hydrogen and nitrogen?

A

Ammonia is formed as a gas, so it is cooled in the condenser so it liquefies and is then removed
- The hydrogen and nitrogen is recycled so nothing is wasted

59
Q

What effect does the iron catalyst have on the reaction between the hydrogen and nitrogen?

A

The iron catalyst makes the reaction reach equilibrium more quickly. Without the catalyst the temperature would have to be raised to get a quick enough reaction lowering the percentage yield even further.

60
Q

When alcohols dissolve in water, is the solution acidic, alkaline or neutral?

A

Neutral

61
Q

Give two uses of alcohols.

A
  1. Ethanol is used in perfumes and alcoholic drinks
  2. Ethanol is used as a fuel in spirit burners
  3. Ethanol, methanol and propanol can be used as solvents
62
Q

What is the functional group in carboxylic acids?

A

COOH

63
Q

What is the functional group in alcohols?

A

OH

64
Q

Give two uses of carboxylic acids.

A
  1. To make ethanoic acid which can dissolved in water to make vinegar
  2. To make soaps and esters
65
Q

What two substances react together to form an ester?

A

An alcohol and a carboxylic acid

66
Q

What catalyst is used in the formation of esters?

A

An acid (such as concentrated sulfuric acid)

67
Q

Explain why the cost of bananas might rise if we keep burning fuel?

A

Fuel is a finite substance because the fossil fuels we are burning to make that fuel is running out. Therefore, fuels like petrol, which is made out of crude oil, will become more expensive as the price for crude oil `becomes more expensive. In turn, the cost of the products that the trucks, planes and ships transport will increase because the petrol they used to transport costs more.

68
Q

How does a catalyst affect overall energy change for a reaction?

A

The activation energy is lowered by the catalyst as it provides a different pathway for a reaction so that the reaction happens more easily and more quickly.

69
Q

What is meant by the term ‘activation energy’?

A

The minimum energy that is required by reacting particles to break their bonds.

70
Q

Give one advantage of using hydrogen as a fuel in a car engine.

A
  1. Hydrogen combines with oxygen in the engine to form water so it is very clean and environmentally friendly.
71
Q

Give some disadvantages of using hydrogen as a fuel in a car engine.

A
  1. It is very hard to store because it is very explosive
  2. You need a special, expensive engine to use and store the hydrogen
  3. You still need to use another energy source to make the hydrogen so it is not as clean
72
Q

What is a fuel cell?

A

An electrical cell that is supplied with a fuel and oxygen and uses energy from the reaction between them to create electricity.

73
Q

Why is the car industry researching fuel cells?

A
  1. Because it doesn’t produce and greenhouse gases , nitrogen oxides or sulfur dioxide so it wouldn’t pollute the environment- good for big cities that suffer from air pollution
  2. It would help countries to become less dependent on crude oil
74
Q

Describe two ways of testing for metal ions.

A
  1. The flame test

2. Identifying the colour of the precipitate using sodium hydroxide

75
Q

What is a mole?

A

A unit of measurement that is used to give an amount of a substance.

76
Q

What do titrations allow you to do?

A

They allow you to find out exactly how much acid is needed to neutralise a quantity of an alkali.

77
Q

How do you calculate the concentration of a substance?

A 
Concentration = number of moles/volume
C = n/v
78
Q

How do you calculate the number of moles in a substance?

A

Number of moles = mass/relative formula mass

N = m/Mr

79
Q

What must happen to break bonds in a reaction?

A

Energy must be supplied to bond-breaking is an endothermic process

80
Q

What must happen for bonds to be formed in a reaction?

A

Energy must be released so bond formation is an exothermic process

81
Q

What is the biggest problem when trying to measure the energy transfer of a reaction?

A

Trying to measure the correct amount that is transferred because there is always an amount of energy that is lost to the surroundings.

82
Q

What are the consequences of using fuels to release energy?

A
  • Burning fuels contributes to global warming
  • Crude oil is running out so fuels will become more expensive
  • Developing alternative energy sources is very expensive
83
Q

What is calorimetry?

A

Measuring the amount of energy released when a fuel is burnt by burning the fuel and using the flame to heat up some water.

84
Q

What is the calculation for measuring the transfer of energy?

A

Energy transferred (J) = mass of water (g) x SHC of water (4.2) x temperature change (C)

85
Q

Using an energy level diagram, how can you tell if the reaction taking place is exothermic or endothermic?

A
  • In an exothermic reaction the products are at a lower energy than the reactants.
  • In an endothermic reaction the products are at a higher energy than the reactants
  • The activation energy will be greater in an exothermic reaction than in an endothermic reaction
  • In an exothermic reaction the energy change will be negative and in an endothermic reaction the energy change will be positive
86
Q

What kind of reaction is hydrogen when it is combined with oxygen?

A

A combustion reaction.

87
Q

Why are fuel cells not likely to mean the end of dependence on fossil fuels or power stations?

A
  • Hydrogen is a gas so it takes up more space to store than a liquid
  • It is very explosive so it is hard to store safely
  • The hydrogen fuel in fuel cells is usually either made from hydrocarbons (fossil fuels) or the electrolysis of water which uses electricity (usually generated by fossil fuels)
88
Q

What flame is produced when each of these metal ions (positive ions) is put in a flame:

a) Lithium
b) Sodium
c) Potassium
d) Calcium
e) Barium

A

a) Crimson flame
b) Yellow flame
c) Lilac flame
d) Red flame
e) Green flame

89
Q

How do you test a solution for carbonates?

A
  • Carbonates react with dilute acids to form carbon dioxide
  • To see if the gas is carbon dioxide, you can bubble it through lime water and if it turns cloudy, you know carbon dioxide has been produced.
90
Q

How do you test for negative ions (halide ions)

A

Add dilute nitric acid to any of the Group 7 elements (the halogens) followed by silver nitrate solution. This forms a coloured precipitate depending on the halogen that was used.

91
Q

What precipitates are produced when testing for negative ions using the following halogens:

a) Chlorine
b) Bromine
c) Iodine

A

a) Chloride gives a white precipitate
b) Bromide gives a cream precipitate
c) Iodide gives a yellow precipitate

Chemistry (5 decks)

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