Paper 4 : C4 + C5 + C6 + C7
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Why do all group 1 elements react in the same way?
They all have one electron in the outer shell
Why do all group 7 elements react in the same way?
They all have 7 electrons in the outer shell
Why do group 2 elements have higher melting points than group 1 elements?
Group 2 elements have a higher charge There is greater attraction between the oppositely charged ions
What is meant by equilibrium when we are discussing reversible reactions?
The rate of the forwards and backwards reaction are equal The concentrations of reactants + products remain constant
Why is universal indicator not used in titrations?
Universal indicator gives a gradual colour change A single indicator needs to be used so there is a sudden colour change
Why does increasing the temperature increase the rate of reaction?
Particles move faster More frequent collisions between reactant particles More successful collisions between reactant particles
What is a limiting reactant?
The reactant that is all used up
Why does increasing the concentration/pressure of a reactant increase the rate of reaction?
More particles in the same volume More frequent collisions
Why is a high percentage yield important for a reaction?
Reduces cost Doesn’t waste starting materials
Why is a high atom economy desirable?
Reduces the production of unwanted products Makes the process more sustainable Maximises profit
How are soluble salts made?
Titration - Alkali added to acid until it is just neutralised Water evaporated
Why is a compromise temperature sometimes used for reversible reactions which are exothermic in the forward direction?
A low temperature would give a high yield However, a low temperature would give a slow rate of reaction.
Why does a powder react faster than a lump of solid?
Powder has a greater surface area Greater frequency of collisions between reactant particles
What effect does a catalyst have on reversible reactions?
It increases the rate of the forward and backwards reactions It doesn’t affect the position of equilibrium
What are the disadvantages of using fuel cells?
Contain poisonous catalysts Pollution is caused by the burning of fossil fuels when making the raw materials for the fuel cell
What are the disadvantages of using fuel cells?
Contain poisonous catalysts Pollution is caused by the burning of fossil fuels when making the raw materials for the fuel cell
Why is a batch process used to make drugs but a continuous process used to make fertilisers?
Drugs are needed in small amounts Fertilisers are used in large amounts
Why is it important that air pollution is controlled?
Prevent harm to living organisms Protect buildings
Explain one advantage and one problem of recycling copper
Saves resources because the ore does not have to be extracted But, copper has to be sorted from other metals
Why is reinforced steel a better construction material than normal concrete?
Steel is strong under tension, whereas concrete is strong under compression Steel is more flexible
What are the advantages of using aluminium rather than steel in car construction?
Aluminium is less dense Aluminium does not corrode
What is a hydrocarbon?
A compound that contains only hydrogen and carbon
What is meant by a saturated compound?
All carbon-carbon bonds are single bonds
What is meant by an unsaturated hydrocarbon?
Contains carbon-carbon double bonds