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The table below gives the electron distributions of atoms of different elements.
[Table_1]
For each of the following, select an element or elements from the table that matches the description. Each element may be selected once, more than once or not at all.
(a) These two elements are in the same group.
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(b) This element forms a fluoride with a formula of the type XF3.
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(c) This element reacts violently with cold water.
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(d) This element has a macromolecular structure similar to that of diamond.
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(e) The only oxidation state of this element is 0.
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(f) This element is bromine.
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(g) This element is a good conductor of electricity.
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520
589
560
(a) Natural gas, which is mainly methane, is a fossil fuel.
(i) What is meant by the term fuel?
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........................................................................................................................ [1]
(ii) Name two other fossil fuels.
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(iii) Name a solid fuel which is not a fossil fuel.
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(b) Fossil fuels are formed by the anaerobic decomposition of organic matter. Anaerobic means in the absence of oxygen.
(i) The organic matter contains hydrogen and carbon. Suggest the products that would be formed if the decomposition occurred in the presence of oxygen.
........................................................................................................................ [2]
(ii) What are the two main disadvantages in the widespread use of fossil fuels?
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........................................................................................................................ [2]
500
541
523
Plant growth is improved by the availability of essential elements, such as nitrogen, and by the soil having a suitable pH.
(a) Nitrogen-based fertilisers are made from ammonia. Ammonia is manufactured by the Haber process.
(i) Describe the Haber process giving reaction conditions and a balanced equation. (Do not discuss reaction rate and yield.)
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[5]
(ii) Fertilisers contain nitrogen. Name the other two elements essential for plant growth commonly found in fertilisers.
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[2]
(b) Crops do not grow well if the soil is too acidic.
(i) One cause of acidity in soil is acid rain. Explain how acid rain is formed.
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[3]
(ii) Name two bases which are used to increase the pH of acidic soils.
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[2]
582
522
582
Propanoic acid is a carboxylic acid. Its formula is CH$_3$–CH$_2$–COOH.
(a) Propanoic acid is the third member of the homologous series of carboxylic acids.
(i) Give the name and structural formula of the fourth member of this series.
name .............................................................................................................................
formula ......................................................................................................................... [2]
(ii) Members of a homologous series have very similar chemical properties. State three other characteristics of a homologous series.
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(b) Carboxylic acids can be made by the oxidation of alcohols.
(i) Draw the structural formula of the alcohol which can be oxidised to propanoic acid. Show all atoms and bonds. [1]
(ii) Name a reagent, other than oxygen, which can oxidise alcohols to carboxylic acids.
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(c) Complete the following equations for some of the reactions of propanoic acid.
The salts of this acid are called propanoates.
(i) zinc + propanoic acid → ........................... .......................... + hydrogen [1]
(ii) calcium oxide + propanoic acid → ........................ ........................ + ...................... [1]
(iii) LiOH + CH$_3$CH$_2$COOH → ............................... + ............................ [1]
(d) A piece of magnesium was added to 100 cm$^3$ of an aqueous acid. The time taken for the metal to react completely was measured. This experiment was repeated using different aqueous acids. The same volume of acid was used in each experiment and the pieces of magnesium used were identical. In one experiment the reaction was carried out at a different temperature.
[Table_1]
Explain the following in terms of collision rate between reacting particles.
(i) Why is the rate in experiment C slower than the rate in experiment A?
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(ii) Why is the rate in experiment B faster than the rate in experiment A?
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......................................................................................................................................... [2]
(iii) Why is the rate in experiment D faster than the rate in experiment A?
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541
536
580
Carbonyl chloride is made from carbon monoxide and chlorine.
$$ ext{CO(g) + Cl}_2 ext{(g)}
ightleftharpoons ext{COCl}_2 ext{(g)}$$
(a) Two methods of preparing carbon monoxide are from methane and oxygen, and from methane and steam.
(i) The reaction between methane and oxygen can also form carbon dioxide. How can carbon monoxide be made instead of carbon dioxide?
............................................................................................................................................................. [1]
(ii) The following reaction is used to make carbon monoxide and hydrogen.
The reaction is carried out at 1100 °C and normal pressure.
$$ ext{CH}_4 ext{(g)} + ext{H}_2 ext{O(g)}
ightleftharpoons ext{CO(g)} + ext{3H}_2 ext{(g)}$$
The reaction is reversible and comes to equilibrium. Suggest why a high temperature is used.
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(iii) What is the disadvantage of using a high pressure for the reaction given in (a)(ii)?
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(b) Chlorine is made by the electrolysis of concentrated aqueous sodium chloride.
Describe this electrolysis. Write ionic equations for the reactions at the electrodes and name the sodium compound formed.
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(c) The structural formula of carbonyl chloride is given below.
Draw a diagram showing the arrangement of the valency electrons around the atoms in one molecule of this covalent compound.
Use ○ to represent an electron from an oxygen atom.
Use × to represent an electron from a chlorine atom.
Use • to represent an electron from a carbon atom. [3]
565
575
548
Scandium, proton number 21, is not a typical transition element.
(a) Scandium is a low density metal which has only one oxidation state in its compounds. Scandium compounds are white solids which form colourless solutions. Titanium, the next metal in the period, is a far more typical transition element. How would the properties of titanium differ from those of scandium? ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
(b) Scandium fluoride is an ionic compound. The valency of scandium in scandium fluoride is three. Draw a diagram which shows the formula of this compound, the charges on the ions and the arrangement of the valency electrons around the negative ions.
Use x to represent an electron from a fluorine atom.
Use o to represent an electron from a scandium atom.
(c) Scandium oxide is insoluble in water. Describe how you could show that it is an amphoteric oxide. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................
600
558
504
(a) The sulfuric acid is added slowly from the burette until the indicator just changes colour. The volume of sulfuric acid needed to just neutralise the lithium hydroxide is noted. Describe how you would continue the experiment to obtain pure dry crystals of hydrated lithium sulfate.
[5]
(b) Using 25.0 cm^3 of aqueous lithium hydroxide, concentration 2.48 mol/dm^3, 2.20 g of hydrated lithium sulfate was obtained. Calculate the percentage yield, giving your answer to one decimal place.
2LiOH + H_2SO_4 \rightarrow Li_2SO_4 + 2H_2O
Li_2SO_4 + H_2O \rightarrow Li_2SO_4.H_2O
Number of moles of LiOH used = .......................
Number of moles of Li_2SO_4.H_2O which could be formed = .......................
Mass of one mole of Li_2SO_4.H_2O = 128 g
Maximum yield of Li_2SO_4.H_2O = ....................... g
Percentage yield = .......................%
[4]
(c) An experiment was carried out to show that the formula of the hydrated salt is Li_2SO_4.H_2O. A sample of the hydrated salt was weighed and its mass recorded. It was then heated and the anhydrous salt was weighed. This procedure was repeated until two consecutive masses were the same. This procedure is called 'heating to constant mass'.
(i) What is the reason for heating to constant mass?
........................................................................................................................[1]
(ii) The mass of the hydrated salt is m_1 and the mass of the anhydrous salt is m_2. Explain how you could show that the hydrated salt has one mole of water of crystallisation per mole of the anhydrous salt.
........................................................................................................................[3]
582
542
571
