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(a) The graph below shows the solubility of sulphur dioxide gas at different temperatures. Use the following in it to answer the questions that follow.
(i) From the graph determine: I The lowest temperature at which 1,000cm3 of solution would contain 116g of sulphur dioxide. II The maximum mass of sulphur dioxide that would dissolve in 15 litres of solution at 100C (ii) Sodium hydroxide reacts with sulphur trioxide according to the following equation. 
Using the information in the graph determine the volume of 2M sodium hydroxide required to completely neutralize on one litre of saturated sulphur dioxide solution 230C. (S=32.0; O; O = 16.0) (3mks) (b) Study the flow chart below and answer the questions that follow. 
Write equation for the reaction taking place at: I The roasting furnace (1mk) II The absorption tower (1mk) III The diluter (1mk) (ii) The reaction taking place in chamber K is 
I Explain why it is necessary to use excess air in chamber K II Name another substance used in chamber K (c) Study the scheme given below and answer the questions that follow: 
(i) Name the reagents used in: Step I……………… (1mk) Step II……………… (1mk) Step IV…………… (1mk) (ii) Write an equation for the complete combustion of CH = CH (1mk) Explain one disadvantage of the continued use of items made from the compound formed in step III (2mks)
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Study the table below and answer the questions that follow:
a) Complete the table by filling in this missing atomic numbers and atomic mass. (2mks) b) Write the electron arrangement for the following ions (2mks) Ca+ P3+ c) What is the melting point of hydrogen in degrees Kelvin? (1mk) d) Which of the allotropes of phosphorous ha a higher density? Explain (2mks) e) The mass numbers of three isotopes of magnesium are 24, 25 and 26. What is the mass number of the most abundant isotope of magnesium? Explain (2mks) f) Give the formula of the compound formed between aluminium and carbon.(1mks) g) Explain the difference in the melting points of magnesium and sodium.(2mks)
Expected Response
a) Give the name of each of the processes described below which takes place when salts are exposed to air for sometime. i) Anhydrous copper sulphate becomes wet (1mk) ii) Magnesium chloride forms an aqueous solution (1mk) iii) Fresh crystals of sodium carbonate, Na2CO3. 10H2O (1mk) b) Write the formula of the complex ion formed in each of the reactions described below. (i) Zinc metal dissolves in hot alkaline solution (1mk) (ii) Copper hydroxide dissolves in excess ammonia solution. (1 mk) (c) A hydrated salt has the following composition by mass. Iron 20.2% Oxygen 23.0%, sulphur 11.5%, water 45.3 %. Its relative formula mass is 278. (i) Determine the formula of the hydrated salt.. (3mks) (Fe=56, S=32; O = 16, H =1) (ii) 6.95gm of the hydrates salt were dissolved in distilled water and the total volume made to 250 cm3 of solution. Calculate the concentration of the salt solution in moles per litre.
Expected Response
a) Study the table below and answer the questions that follow
i) Which of the compounds is a solid at 10.00C? Explain (1mk) ii) Choose two compounds which are members of the same homologous series and explain the difference in their melting points. (3mks) iii) The compound C3H8O is an alcohol. How does its solubility in water differ from the solubility of C5H12 in water? Explain. (2mks) b) Complete combustion of one mole of a hydrocarbon produced four moles of carbon dioxide and four moles of water only. i) Write formula of the hydrocarbon (1mk) ii) Write the equation for the combustion reaction: (1mk) c) In a reaction, an alcohol J was converted to a hex- 1 – ene. i) Give the structural formula of the alcohol J ii) Name the reagent and conditions necessary for the reaction in c (i) above d) Compound K reacts with sodium hydroxide as shown below? (1mk) 
i) What type of reaction is represented by the equation above? (1mk) ii) To what class of organic compounds does K belong? (1mk)
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The extraction of aluminium from it s ore takes place in two stages, purification stage and electrolysis stage. The diagram below shows the set – up for the electrolysis stage
a)
i) Name the ore from which aluminium extracted. (1mk) ii) Name one impurity, which is removed at the purification stage.(1mk) b) i) Label on the diagram each of the following i) Anode ii) Cathode iii) Region containing the electrolyte. ii) The melting point aluminium oxide is 20540C, but electrolysis is carried out between 800 – 9000C. i) Why is the electrolysis not carried out at 20540C (1mk) ii) What is done lower the temperatures? (1mk) iii) The aluminium which is produced is tapped off as aliquid. What does this suggest about it smelting point? (1mk) c) A typical electrolysis cell uses current of 40,000 amperes.Calulate the mass (in kilograms) of aluminium produced in one hour) (3mks)
Expected Response
a) The diagram below shows incomplete set – up of the laboratory and preparation collection of chlorine gas. Study it and answer the questions that follow.
i) Complete the set – up to show how dry chloride gas may be collected.
ii) The equation for the redox reaction that takes place is 
Explain, using oxidation numbers, which species is reduced (2mks)
iii) What is the purpose of water in flask L? (1mk) b) Study the diagram below and answer the questions that follow. 
When some hydrogen chlorides gas is allowed into water and the mixture stirred, the bulb lights and gases X and Y are formed.
i) Name: Gas X Gas Y ii) Explain why the bulb does not light before the hydrogen chloride gas is let into water. (2mks) iii) Explain using equations why the volume of gas X is less than that of gas (2mks)
Expected Response
Sodium thiosulphate solution reacts with dilute hydrochloric acid according to the following equation.
In an experiment to study how the rate of reaction varies withconcentration, 10cm3 of 0.4M sodium thiosulphate was mixed with 10cm3. Of 2M hydrochloric acid in a flask. The flask was placed in a white paper marked with across X.The time taken for the cross X become invisible when viewed from above was noted and recorded in the table below. The experiment was repeated three times as the temperature using the volumes in the table and the results recorded as shown in the table below. 
a) i) On the grid below, plot a graph of the volume of thiosulphate (Vertical axis) against time taken for the cross (X) to become invisible) ii) From the graph determine how long it would take for the cross to become invisible if the experiment was done. (3mks) i) Using 6cm3 of the 0.4M thiosulphate (1mk) ii) Using 6cm3 of 0.2M thiosulphate solution (1mk) b) i) Using values for experiment I.Calculate i) Moles of thiosulphate used (1mk) ii) Moles of hydrochloric acid used (1mk) ii) Explain which of the two reactants in experiment I controlled the rate of the reaction? Explain (1mk) c) Give two precautions which should be taken in experiment I controlled the rate of the reaction? Explain (2mk)
Expected Response
Write an equation for the reaction that takes place when carbon monoxide gas is passed over heated lead (II) oxide. (1mks)
Study the chart below and a answer the questions that follow:
a) Identify
i) The metal ions in solution K (1mks) ii) The white precipitate L (1mk)
b) What property of white precipitate L is illustrated in steps I and II. (1mk)
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A mixture of pentane and pentanoic acid was shaken with 0.1M sodium hydroxide solution and let to separate as shown in the diagram below
Name the main component in layer W. Give a reason for the answer (2mks)
Expected response
Pentane: It is non poler and will not react with sodium Hydroxide solution which is an ionic compound. In an experiment, 2.4g of sulphur was obtained by reacting hydrogen sulphide and chorine as shown by the equation below: H2S(g) + Cl2(g) → S(s) + 2HCl(g) (a) Which of the reactants acts as a reducing agent in the above reaction? Explain. (1 mk) (b) Given that the yield of sulphur in the above reaction is 75%, calculate the number Of moles of H2S(g) used in the reaction (S=32.0)
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Study the flow chart below and answer the questions that follow
a) Name
i) Compound T (1mk) ii) Gas U (1mk) b) Give a chemical test that you could use to identify gas U (1mk)
expected response
a)
i) Iron (II) Suphide ii) Hydrogen Sulphide
b) Darker paper soaked in lead acetate
Explain how you would obtain solid carbonate from a mixture of lead carbonate and sodium carbonate powders. (3mks)
Expected Response
Dissolve in water, filter to remove lead carbonate as a residue, evaporate filter to saturation and allow to cool. Crystallization to take place. Filter the crystals and dry. Evaporate to dryness
The diagram below represents a set-up that was used to react lithium with water study it and answer the questions that follow:
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Chlorine and iodine are elements in the same group in the periodic table. Chlorine gas is yellow white aqueous, iodine; I2(aq) is brown. a) What observation would be made if chlorine gas is bubbled through aqueous sodium iodide? Explain using and ionic equation. (2mks) b) Under certain conditions chlorine and iodine react to give iodine chloride, ICl3(s)- What type of bonding would you expect to exist in iodine trichloride? Explain (1mk)
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December 2024
AuthorMaurice Atika is a teacher and a netprenuer. |
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