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Chemistry > Topic 7: Groups In The Periodic Table And Rates Of Reaction > Flashcards

Topic 7: Groups In The Periodic Table And Rates Of Reaction Flashcards

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1
Q

How is the periodic table arranged?

A

It is arranged so that elements in the same vertical column or group have similar chemical and physical properties and show tends in properties.

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2
Q

What properties do the alkali metals have?

A

The alkali metal in group 1 have similar physical properties to other metals- they are all malleable and conduct electricity. All alkali metals have relatively low melting, are soft and easily cut. They are also very reactive and readily form compounds with non-metals.

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3
Q

Do all alkali metals oxidise easily?

A

All alkali metals oxides and burn brightly on air.

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4
Q

What is the trend in reaction for the alkali metals?

A

The reactivity increases down the group.

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5
Q

What are the alkali metals? (In order of least reactive to most reactive)

A 
Lithium
Sodium
Potassium
Rubidium
Caesium
Francium
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6
Q

How do the first 3 alkali metals react with water?

A

Lithium + water (bubbles fiercely on the surface)
Sodium + water (melts in to a ball and fizzes about the surface)
Potassium + water (bursts into flames and flies about surface)

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7
Q

What does the electron configuration have to do with the reactivity if alkali metals?

A

As you down the alkali metals/group 1 the atoms become larger because an extra electron shell is added to each period. The force of attraction between the positive nucleus (the protons) and negative electrons gets weaker as hey become further apart. Therefore the further down you go the more reactive because they have a weaker attraction and therefore can loose electron/react more easily.

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8
Q

What are the halogens?

A

These are the elements in group 7.

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9
Q

What is a diatomic molecule?

A

Two atoms chemically binder together.

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10
Q

What are the chemical properties of the halogens?

A
  • exist as diatomic molecules, with 2 atoms held together by a single covalent bond.
  • non metallic elements
  • poor conductors of heat and electricity
  • toxic and corrosive
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11
Q

What are the physical properties of the halogens?

A

As you go down the group their melting point, boiling point and densities all increase.

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12
Q

What do the first 3 halogens look like?

A
  • chlorine = green gas
  • bromine = brown liquid
  • Iodine = purple/ black solid
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13
Q

What do halogens produce when they react with metals?

A

They form ionic compounds called salts, which contain halide ions.

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14
Q

What are halide ions?

A

A compound formed between a halogen and another element such as a metal and hydrogen.

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15
Q

What are the uses of haloed salts?

A

Sodium halide salts can be used as…

  • sodium chloride = table salt
  • sodium bromide = used in a disinfectant for swimming pools
  • sodium fluoride = found in many tooth pastes
  • sodium iodide = added to table salt to prevent iodine deficiency
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16
Q

What uses to halogens have?

A
  • they can all be used as disinfectant or bleach to kill microbes.
  • they can all remove colour from materials (e.g bleach)
  • chlorine is used in swimming pools and many types of bleaches to kill microbes.
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17
Q

What is the test for chlorine?

A

If damp litmus paper is placed in liquid chlorine it first turns red and then bleaches white.

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18
Q

What happened when halogens react with hydrogen?

A

They form hydrogen halides, which dissolve in water to form acidic solutions. E.g hydrochloric acid.

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19
Q

How is hydrochloric acid formed?

A

1- hydrogen and chlorine molecules collide and the covalent bonds holding the atoms together break. (They explode as they react with each other)

2-covalent bonds form between hydrogen and chlorine atoms, making a new compound, hydrogen chloride.

3-when hydrogen chloride dissolved in water the molecules break up into to 2 ions H+ and Cl-.

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20
Q

What are the halogen elements in order of reactivity (most reactive to least reactive)?

A 
Chlorine 
Bromine 
Iodine 
Fluorine 
Tennessine
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21
Q

What is the reactivity of the halogens?

A

Chlorine is the most reactive and tennessine is the least due to the electron shells.

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22
Q

How do the halogens react when heated with iron wool?

A

Fluorine - bursts into flames
Chlorine - glows brightly
Bromine - glows dull red
Iodine - changes colour

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23
Q

How can the reactivity of the halogens be worked out?

A

Using displacement reactions. A more reactive halogen replaces a less reactive halogen from a halide compound.

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24
Q

What is a displacement reaction?

A

A reaction where a more reactive element takes the place of a less reactive element in an ionic compound.

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25
Q

How can you explain the trend in reactivity for the halogens?

A

Group 7 elements gain one electron when they react. Down the group the distance between the outmost shell and the nucleus containing the positive protons increases. This ems system the force of attraction between the positive nucleus and the incoming negative electron decreases so the ions do not form so easily and therefore the reactivity decreases.

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26
Q

What is an oxidation reaction?

A

When a metal reacts with oxygen it loses electron so we can define this as an oxidation reaction as the metal looses electrons.

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27
Q

What is a reduction reaction?

A

When a metal reacts with oxygen and gains electrons.

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28
Q

What does ‘OILRIG’ mean?

A

Oxidation Is Loss Reduction Is Gain

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29
Q

What is redox reaction?

A

When oxidation and reduction reactions occur at the same time in a displacement reaction.

30
Q

What are some of the properties of noble gases?

A

They….
-are colourless
-have very low melting and boiling points
-are poor conductors of heat and electricity
-they are inert (they are so not react with easily)
-all exist as single atoms, because they do not form bonds easily with other atoms as they are inert.
(They have a trend in physical properties)

31
Q

What does inert mean?

A

This means un-reactive so they do not react easily with other elements such as noble gases.

32
Q

Why are noble gases inert?

A

Because they have a full outer shell of electrons so do not need to react to become more stable as they already are.

33
Q

What are the noble gases?

A 
Helium
Neon
Argon 
krypton
Xenon
34
Q

The noble gases were found at the end of the 19th century why were the noble gases so hard to find?

A

Difficult to detect because they do not react with anything and there are only very small amounts of them in our atmosphere.

35
Q

How is the noble gas krypton used?

A

Used in photography lighting. It produces a brilliant white light when electricity is passed through it.

36
Q

How is the noble gas neon used?

A

Produces a distinctive red-orange light when electricity is passed through it. This property makes it useful for making long lasting illuminating signs.

37
Q

How is the noble gas argon used?

A

Argon is denser than air. It is added to the space above the wine in wine barrels to stop oxygen in the air reacting with the wine.

38
Q

How is the noble gas helium used?

A

Helium has a very low density and is non-flammable so is used in weather balloons and airships.

39
Q

How do atoms become more stable?

A

By gaining, loosing or sharing electrons to get an electron configuration like a noble gas.

40
Q

What is always formed in a chemical reaction?

A

A new substance, a product(s).

41
Q

Define what is meant by the rate of reaction?

A

The speed in which reactants are turned into products.

42
Q

How can you control the rate of a reaction?

A

We can control rates of reactions by alternating variables, such as the concentration of solutions and the size of pieces if solid reactant.

43
Q

How can you investigate the rate if reactions?

A

You need to be able to measure how the amount of reactants or products change with time. This can be plotted on a graph. The gradients/slope of graph indicated the rate: steeper the gradients after the reaction.

44
Q

Why are reactions fastest at the start?

A

Because this is when the concentration of the reactants is greatest.

45
Q

How can you monitor the rates of reaction?

A

You can minter rates by measuring changes in mass or volume of the reactants or products.

46
Q

When reacting magnesium sulphate and sulphuric acid which react faster and why? Magnesium ribbon of magnesium granules?

A

Magnesium granules because they are smaller pieces of solid than the ribbon and therefore react more quickly.

47
Q

What is meant by activation energy?

A

The minimum amount of energy required to start a reaction.

48
Q

What must happen to particles for chemical reactions to occur?

A

The reactant particles must collide with enough energy to react. During successful collision the activation energy helps break bonds, so that the atoms can be rearranged to make new substances. (The products of the reactants)

49
Q

How can reaction rates be increased?

A

Reaction rates are increased when when the energy of collisions is increased, and when the frequency is increased (number of collapses in a certain time).
More collisions occur if the particles are closer together or moving faster.

50
Q

What is needed for more collisions to be successful?

A

More collisions will be successful if more of the particles have the activation energy required.

This is because the particles in any substance have a range of energies and only those with enough energy can react.

51
Q

How would changing the concentration of a solution have an effect on the rate of reaction?

A

Increasing the concentration of solutions increases the rate of reaction. This is because there are more reacting particles in the same volume so collisions occur more often.

52
Q

How would changing the temperature have an effect on the rate of reaction?

A

Increasing the temperature increases the rate of reaction. This is because the reactant particles speed up and therefore have more energy. This means they collide more often and more particles have enough energy to react when they collide.

53
Q

How would changing the surface have an effect on the rate of reaction?

A

Increasing the Surface Area:Volume ratio by decreasing the size of the solid pieces while keeping the total volume of the solid the same, increases the rate of reactions. This is because there is more surface for collisions to happen so they occur more often.

54
Q

How would changing the pressure of gases have an effect on the rate of reaction?

A

Increasing the pressure of gases, increases the rate of reactions. This is because the reactant particles are squeezed closer together so reactions occur more often.

55
Q

What are catalysts?

A

Substances that speed up chemical reactions without being chemically changed themselves or altering the product made in reaction.

56
Q

What are the benefits if using catalysts in industry?

A
  • make industrial processes more profitable, by making products more quickly and by allowing reactions to occur at lower temperatures, which saves costs.
  • catalysts don’t usually need to be replaced because they are not used up in reactions.
57
Q

Why are catalysts used?

A

Because they provide an alternative reaction route which requires less activation energy.

58
Q

What are reaction profiles?

A

A diagram to show how energy stored in a substance changes during the course of a chemical reaction.

59
Q

Do catalysts alter the overall change in energy?

A

No. However, they since the pay use less energy to start the reaction, more reactant molecules have enough energy and so more collisions are successful. This therefore means the reaction is faster.

60
Q

How does a catalytic converter work in a car and what is its purpose?

A

Catalysts are platinum and palladium in car exhausts. Their presence lowers the activation energy needed to convert harmful gases into harmless gases. The metals used are expensive but don’t need to be replaced as they are not used up.

61
Q

What is an exothermic reaction?

A

Energy is transferred from stores in chemical bonds to the surroundings.

62
Q

What is an endothermic reaction?

A

Energy is transferred from the surrounding to the stores in chemical bonds.

63
Q

During chemical reactions how is energy transferred between the reacting substances and surroundings?

A

By heating, particularly if it’s in a solution. The stored thermal (heat) energy in the solution increases during an exothermic reaction, and it decreases during an endothermic reaction.

64
Q

How can you determine if a reaction in a solution is endothermic or exothermic?

A
  • temperature increases in an exothermic reaction.

- temperature decreases in a endothermic reaction.

65
Q

Give 2 examples of an exothermic reaction:

A
  • neutralisation reaction between and acid and a base.
  • displacement reaction, the reaction between a metal and a compound of a less reactive metal, or between a halogen and a compound of a less reactive halogen.
66
Q

Are precipitation reactions exothermic or endothermic reactions?

A

They can be both

67
Q

Give 2 examples of endothermic reactions:

A
  • melting an ice cube
  • evaporating liquid water
  • photosynthesis
68
Q

What is a precipitation reaction?

A

A reaction in which an insoluble product and is formed from 2 soluble reactants.

69
Q

Give examples of reactions that require low activation energy and high activation energy:

A

Precipitation and neutralisation reactions have low activation energies and start as soon as the reactants are mixed.
Combustion reaction have higher activation energies. These reactions need energy from a spark or flame to start.

70
Q

What energy is transferred when bonds between particles break and form?

A

Energy is transferred to the reactants to break their bonds so breaking bonds is endothermic.

Energy is transferred to the surroundings as bonds form, so making bonds is exothermic.

71
Q

What happens to bonds during chemical reactions?

A

During a chemical reaction bonds in the reactants break and new bonds are created from the products.

72
Q

When is a reaction exothermic…..and when is a reaction endothermic…..?

A

A reaction is exothermic if more energy is given out making the binds than is needed to break the bonds. A reaction is endothermic if less energy is given out making bonds than is needed to break bonds.

Chemistry (14 decks)

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