C2.5

Question	Answer
Which ions are produced by acids when they are added to water?	Hydrogen ions, H+(aq)
What is an alkali?	A soluble base or a substance that produces hydroxide ions in solution OH-(aq)
Which indicators can tell us the pH of a solution?	Universal indicator or full-range indicators
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
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
Name the products when nitric acid reacts with magnesiu	Magnesium nitrate and hydrogen
Name the products when hydrochloric acid reacts with copper hydroxide	Copper chloride chloride and water
What compound is produced in every neutralised reaction?	Water H2O
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
What must be done to ionic compounds before they can be electrolysed?	They must be melted or dissolved in water
Molten zinc chloride is electrolysed. Name the substances produced at the positive electrode	Chlorine
Molten zinc chloride is electrolysed. Name the substances produced at the negative electrode	Zinc
What type of change happens at the negative electrode when sodium ions become sodium atoms?	Reduction or positive sodium ions gain electrons
Complete the half equation for the formation of chlorine at a positive electrode: 2Cl- -> .... + ....	2Cl- -> Cl2 + 2e-
Name the products at the positive electrodes when aqueous copper sulfate solution is electrolysed using carbon electrodes	Oxygen
Name the products at the negative electrodes when aqueous copper sulfate solution is electrolysed using carbon electrodes	Copper
Why is aluminium oxide mixed with with cryolite in the electrolysis cell?	To lower the melting temperature
What are the final products of the electrolysis cell?	Aluminium and carbon dioxide
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 reactive than hydrogen
Why is the electrolysis of brine an important industrial process?	It's (three) products have many uses or can be used in many ways
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)
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)
Dilute nitric acid is added to sodium hydroxide solution. What type of substance is sodium hydroxide?	An alkali
Dilute nitric acid is added to sodium hydroxide solution. What type of reaction happens?	Neutralisation
Dilute nitric acid is added to sodium hydroxide solution. Why is an indicator used to show when the reaction is complete?	There is no visible change and it will show when the pH is 7
Dilute nitric acid is added to sodium hydroxide solution. Write a word equation for the reaction	Nitric acid + sodium hydroxide -> sodium nitrate + water
Describe the main steps to make zinc sulfate crystals from zinc oxide and dilute sulphuric acid	Add zinc oxide, a little at a time, to dilute sulfuric acid, until there is an excess, filter off the excess, evaporate some of the water, leave to cool and crystallise
Describe how you could make some insoluble lead sulfate from solutions of lead nitrate and sodium sulfate	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
Why are some items of jewellery made of gold-plated nickel?	Less expensive than pure gold, to improve appearance, so they do not corrode (or cause allergic reactions)
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)
Aluminium is manufactured from aluminium oxide, Al2O3, which is inexpensive. Why is manufacturing aluminium an expensive process?	It needs: Large amounts of electricity, high temperature to melt the aluminium oxide
Aluminium is manufactured from aluminium oxide, Al2O3, which is inexpensive.	To lower the melting/operating temperature (of the electrolyte
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 reduced, to sodium atoms/metal. At the positive electrode: chloride ions lose electrons, are oxidised, to chlorine atoms, which form chlorine molecules/gas
Write half equations for the reactions at the electrodes when magnesium chloride solution MgCl2(aq) is electrolysed using carbon electrodes	At the negative electrode: 2H+ + 2e- --> H2 At the positive electrode: 2Cl- --> Cl2 + 2e-

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	Created by Mel Hughes over 8 years ago