Chemistry

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What two types of measurement must be made to find the average rate of a reaction?
amount of reactan used/time OR amount of product formed/time
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How can we use a graph of amount of product against time to tell us te rate of the reaction at a given time?
The gradient of the line at a given time gives the rate at that time
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List the factors that increase the rate of a reaction
Temperature, concentration of solutions, pressure of gases, surface area of solids, using a catalyst
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Why do powders react faster than large pieces of solid?
Powders have greater surface area than large lumps of solid, and this increases the chance of collisions.
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Why can catalysts be used over and over again?
They remain at the end of a reaction or they are not used up in the reaction.
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Why do different reactions need different catalysts?
Catalysts often work with only one type of reaction.
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What are the benefits of using catalysts in industrial processes?
They reduce the energy needed and the time needed, and so reduce costs. They may reduce the amount of fossil fuel used and so conserve resources and reduce pollution
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Give one disadvantage of transition metal catalysts.
They may be toxic or expensive
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What two areas of research offer possibilities for new or better catalysts?
Nanoscience and enzymes
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Why does adding water to anhydrous copper sulfate cause the mixture to get hot?
It is an exothermic reaction
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Suggest one advantage and one disadvantage of a re-usable hand warmer compared with a single use hand warmer.
One advantage e.g. less waste, less materials/resources used; one disadvantage e.g. has to be heated or needs energy so it can be used again, shlower reaction, smaller temperature rise.
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Suggest one advantage and one disadvantage of a chemical cold pack compared with using an ice pack.
One advantage: e.g. can be used anywhere, can be stored easily (ice needs to be made and/or stored in special equipment?; one disadvantage e.g. can only be used once, more waste, possibly more hazardous than ice.
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What is meant by the 'activation energy' of a reaction?
The minimum energy that particles must have for collisions to produce a reaction
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Name two types of reaction that are exothermic.
Two examples: e.g. combustion, oxidation, neutralisation
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Which ions are produced by acids when they are added to water?
Hydrogen ions
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What is an alkali?
A soluble base or substance that produces hydroxide ions in solution, OH-(aq)
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Name a metal other than zinc that can safely react with an acid to produce a salt.
Any metal that is more reactive than hydrogen, but less reactive than calcium, e.g. lead, tin, iron, aluminium, magnesium.
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Why do we add excess of the base when making a salt?
To use up all of the acid or to neutralise all of the acid
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What compound is produced in every neutralisation reaction?
Water, H(2)O
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Zinc Carbonate is insoluble in water. What would happen when sodium carbonate solution is added to zinc sulfate solution?
Zinc carbonate would be produced as a precipitate or solid, sodium sulfate would remain in the solution
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What must be done to ionic compounds before they can be electrolysed?
They must be melted or dissolved in water
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Molten zinc chloride is electrolysed. Name the substances produced (a) at the positive electrode and (b) at the negative electrode.
(a)Chlorine (b)Copper
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What type of change happens at the negative electrode when sodium ions become sodium atoms?
Reduction or positive sodium ions gain electrons
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Complete the half equation for the formation of Chlorine at a positive electrode: 2CL- --> ... + ...
2CL- --> Cl(2) +2e-
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Name the products at (a) the positive and (b) the negative electrodes when aqueous copper sulfate solution is electrolsed using carbon electrodes.
(a) Oxygen (b) Copper
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Why is alumniium oxide mixed with cryolite in the electrolysis cell?
To lower the melting temperature
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What are the final products of the electrolysis cell?
Aluminium and Carbon Dioxide
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Comple the half equation for the formation of Oxygen at the positive electrode: 2O(2)-(l) --> ... + ...
2O(2)-(l) --> 2O(2)(g) +4e-
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Complete the half equation for the formation of Aluminium at the negative elctrode: ... + ... --> Al(l)
Al(3)+(l) + 3e- --> Al(l)
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Why is hydrogen produced when sodium chloride solution is electrolysed?
The solution contains hydrogen ions which are discharged in preference to sodium ions because sodium is more reactibe than hydrogen
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Why is electrolysis of brine an important industrial process?
Its (three) products have many uses or can be used in many ways
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Why are some knives, forks and spoons silver-plated?
To make them look attractive, to protect the metal from corrosion, to reduce the cost (of making the items from pure silver)
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Describe how you would silver plate a small piece of copper jewellery.
Pass electricity through a cell with the item of jewellery as the negative electrode, the positive electrode made of silver and containing a solution of a silver salt (e.g. silver nitrate solution) (as the electrolyte).
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What type of substance is sodium hydroxide?
An alkali
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Describe the main steps to make zinc sulphate crystals from zinc oxide and dilute sulphuric acid.
Add zinc oxide, a little at a time, to dilute sulphuric acid, until there is an excess, filter off the excess, evaporate some of the water, leave to cool and crystallise
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Describe how you could make some insoluble lead sulphate from solutions of lead nitrate and sodium sulphate.
Mix the two solutions, filter the mixture or leave to settle and decant or centrifuge and decant to separate the solid (precipitate). Then wash with distilled water and dry
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Name the products when sodium chloride solution is electrolysed and give one use for each.
Hydrogen, chlorine and sodium hydroxide. A use for each: e.g. hydrogen; to make hydrochloric acid, margarine manufacture, fuel; Chlorine: to make bleach, plastics; sodium hydroxide: to make soap, paper, as a cleaning agent (ovens/drains)
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Aluminium is manufactured from aluminium oxide, Al(2)O(3), which is inexpensive. (a) Why is manufacturing aluminium an expensive process? (b) why is cryolite used in the process to make aluminium?
(a) It needs: large amounts of electricity, high temperature to melt the aluminium oxide. (b) to lower the melting/operating temperature (of the electrolyte)
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Explain as fully as you can what happens at the electrodes when molten sodium chloride is electrolysed.
At the negative electrode: sodium ions gain electrons, are reduce, to sodium atoms/metal. At the positive electrode: chloride ions lose electrons, are oxidised, to chlorine atoms, which form chlorine molecules/gas.
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How can we use a graph of amount of product against time to tell us te rate of the reaction at a given time?

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The gradient of the line at a given time gives the rate at that time

Card 3

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List the factors that increase the rate of a reaction

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Card 4

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Why do powders react faster than large pieces of solid?

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Card 5

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Why can catalysts be used over and over again?

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