0620_w05_qp_3
A paper of Chemistry, 0620
Questions:
7
Year:
2005
Paper:
3
Variant:
0
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1
For Examiner's Use The structure of a typical ionic compound is a regular arrangement of positive and negative ions. + – + – + – + – + – + – + – + – – + – + + – + – What is the name of this regular arrangement of particles? Give two physical properties of ionic compounds. Ions are formed by electron loss or gain. The electron distribution of a magnesium atom is 2 + 8 + 2 and of a nitrogen atom is 2 + 5. Give the formula of the magnesium ion. Give the formula of the nitride ion. What is the formula of the ionic compound, magnesium nitride? In this compound there is an ionic bond. Why are the two ions attracted to each other?
2. Atoms, elements and compounds  →  2.4. Ions and ionic bonds
3. Stoichiometry  →  3.1. Formulae
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2
For Examiner's Use Ethanoic acid is a colourless liquid at room temperature. It has the typical acid properties and forms compounds called ethanoates. A pure sample of ethanoic acid is slowly heated from 0oC to 150oC and its temperature is measured every minute. The results are represented on the graph below. temperature time A B C D E F Name the change that occurs in the region D to E. What would be the difference in the region B to C if an impure sample had been used? Sketch on the graph how the line would continue if the acid was heated to a higher temperature. For Examiner's Use Complete the following table that compares the separation and movement of the molecules in regions C to D with those in E to F. C to D E to F separation (distance between particles) movement of particles random and slow Can particles move apart to fill any volume? Complete the word equations for the reactions of ethanoic acid. calcium + ethanoic acid + + ethanoic acid zinc ethanoate + water Write the symbol equation for the reaction between ethanoic acid and sodium hydroxide.
11. Organic chemistry  →  11.7. Carboxylic acids
7. Acids, bases and salts  →  7.1. The characteristic properties of acids and bases
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For Examiner's Use Reversible reactions can come to equilibrium. They have both a forward and a backward reaction. When water is added to an acidic solution of bismuth(chloride, a white precipitate forms and the mixture slowly goes cloudy. BiC3+ H2OBiOC+ 2HCcolourless white forward backward Explain why the rate of the forward reaction decreases with time. Why does the rate of the backward reaction increase with time? After some time why does the appearance of the mixture remain unchanged? When a few drops of concentrated hydrochloric acid are added to the cloudy mixture, it changes to a colourless solution. Suggest an explanation. For Examiner's Use Both of the following reactions are reversible. N2+ O2reaction 1 2NO2NO+ O2reaction 2 2NO2Suggest a reason why an increase in pressure does not affect the position of equilibrium for reaction 1. What effect would an increase in pressure have on the position of equilibrium for reaction 2? Give a reason for your answer.
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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For Examiner's Use The alcohols form a homologous series. The first member is methanol and the fourth is butanol. CH3 CH2 CH3 OH CH2 CH2 OH methanol butanol Give two general characteristics of a homologous series. Calculate the mass of one mole of the C8 alcohol. Give the name and structural formula of the third member of this series. name structural formula The structural formula of the fifth member, pentan-1-ol, is drawn below. CH3 CH2 CH2 CH2 CH2 OH Draw the structural formula of an isomer of this alcohol. For Examiner's Use Predict the names of the productformed when pentan-1-ol • reacts with an excess of oxygen, and • is dehydrated to form an alkene, • is oxidised by acidified potassium dichromate(.
11. Organic chemistry  →  11.2. Naming organic compounds
11. Organic chemistry  →  11.1. Formulae, functional groups and terminology
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For Examiner's Use Strontium and zinc are both metals with a valency of 2. Strontium is more reactive than zinc. Its chemistry is similar to that of calcium. Complete the following table that shows the number of protons, electrons and neutrons in each particle. particle protons electrons neutrons 88Sr 90Sr 65Zn2+ Explain why 88Sr and 90Sr are isotopes. Complete the electron distribution of an atom of strontium. + + + + The major ore of zinc is zinc blende, ZnS. Describe how zinc is extracted from zinc blende. Give a use of zinc. For Examiner's Use The major ore of strontium is its carbonate, SrCO3. Strontium is extracted by the electrolysis of its molten chloride. Name the reagent that will react with the carbonate to form the chloride. The electrolysis of molten strontium chloride produces strontium metal and chlorine. Write ionic equations for the reactions at the electrodes. negative electrode positive electrode One of the products of the electrolysis of concentrated aqueous strontium chloride is chlorine. Name the other two. Both metals react with water. Write a word equation for the reaction of zinc and water and state the reaction conditions. word equation conditions Write an equation for the reaction of strontium with water and give the reaction condition. equation condition
9. Metals  →  9.4. Reactivity series
4. Electrochemistry  →  4.1. Electrolysis
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6
For Examiner's Use The following method is used to make crystals of hydrated nickel sulphate. An excess of nickel carbonate, 12.0 g, was added to 40 cm3 of sulphuric acid, 2.0 mol/dm3. The unreacted nickel carbonate was filtered off and the filtrate evaporated to obtain the crystals. NiCO3 + H2SO4 NiSO4 + CO2 + H2O NiSO4 + 7H2O NiSO4.7H2O Mass of one mole of NiSO4.7H2O = 281 g Mass of one mole of NiCO3 = 119 g Calculate the mass of unreacted nickel carbonate. Number of moles of H2SO4 in 40 cm3 of 2.0 mol/dm3 acid = 0.08 Number of moles of NiCO3 reacted = Mass of nickel carbonate reacted = g Mass of unreacted nickel carbonate = g The experiment produced 10.4 g of hydrated nickel sulphate. Calculate the percentage yield. The maximum number of moles of NiSO4 .7H2O that could be formed = The maximum mass of NiSO4 .7H2O that could be formed = g The percentage yield = % In the above method, a soluble salt was prepared by neutralising an acid with an insoluble base. Other salts have to be made by different methods. Give a brief description of how the soluble salt, rubidium sulphate could be made from the soluble base, rubidium hydroxide. For Examiner's Use Suggest a method of making the insoluble salt, calcium fluoride.
7. Acids, bases and salts  →  7.3. Preparation of salts
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For Examiner's Use In 1909, Haber discovered that nitrogen and hydrogen would react to form ammonia. The yield of ammonia was 8%. N2 + 3H2 2NH3 the forward reaction is exothermic catalyst platinum temperature 600 oC pressure 200 atm Describe how hydrogen is obtained for the modern process. What is the catalyst in the modern process? Explain why the modern process, which uses a lower temperature, has a higher yield of 15%. Complete the following table that describes the bond breaking and forming in the reaction between nitrogen and hydrogen to form ammonia. bonds energy change /kJ exothermic or endothermic 1 mole of N N broken +945 3 moles of broken +1308 6 moles of N – H formed -2328 Explain, using the above data, why the forward reaction is exothermic.
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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