A volume of 80cm3 of a mixture of propane (C3H8) and oxygen were ignited in an experiment. The products were cooled and passed through an aqueous sodium hydroxide. The final volume was reduced by 30cm3a) Write the equation for the combustion of propane (1mk)b) Determine the volume of;i) The component of the original mixture (2mks)ii) Residual oxygen (1mk)
(a) The diagram in Figure 4 was used to prepare hydrogen chloride gas which was passed over heated iron powder.
(i) Give a pair of reagents that will produce hydrogen chloride gas in flask A.
(ii) Name the substance in flask B. (iii) State the observation made in the combustion tube. (iv) Write an equation for the reaction in the combustion tube. (v) Describe a chemical test for hydrogen chloride gas. (b) (1) Identify the gas that burns at the jet. (ii) Explain why the gas in (b) (I) is burned. (c) Give reasons why excess hydrogen chloride gas is dissolved using the funnel arrangement. (d) State what will be observed when the reaction in the combustion tube is complete. (e) Another experiment was carried out where hydrogen chloride gas was bubbled through methylbenzene and water in separate beakers. The resulting solutions were tested with blue litmus papers and marble chips. (i) Write the observations made in the following table. 
(ii) Explain the observations in (e) (i).
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An experiment was carried out to prepare crystals of magnesium sulphate. Excess magnesium powder was added to 100 cm3 of dilute sulphuric (VI) acid in a beaker and warmed until no further reaction took place. The mixture was filtered and the filtrate evaporated to saturation, then left to cool for crystals to form.
(a) (i) Write an equation for the reaction. (ii) Explain why excess magnesium powder was used. (iii) State how completion of the reaction was determined. (iv) What is meant by a saturated solution? (v) Explain why the filtrate was not evaporated to dryness. (b) When bleaching powder, CaOCl2, is treated with dilute nitric(V) acid, chlorine gas is released. This reaction can be used to determine the chlorine content of various samples of bleaching powders and liquids. (i) Write an equation for the reaction of nitric(V) acid with bleaching powder. (ii) Calculate the volume of chlorine produced when 10g of CaOCl2 is treated with excess nitric (v) acid. (Ca = 40.0; 0 = 16.0; Cl = 35.5; 1 mole of gas occupies 22.4dm3 at s.t.p) (c) Apart from use of chlorine gas in bleaches and water treatment, state two other uses of chlorine gas.
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Distinguish between empirical and molecular formula of a compound.
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(NH4)2HPO4 is a fertilizer used by farmers to boost their crop production.
(a) Calculate the mass of phosphorus in a 20 kg packet 14.0; H = 1.0; P = 31.0; 0 16.0) (b) State one advantage of this fertilizer, (NH4)2HPO4 over urea CO(NH2)2
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(a) Zinc reacts with hydrochloric acid according to the following equation.
Identify the reducing agent. Give a reason for the answer.
(b) Iron sheets are dipped in molten zinc to prevent rusting. Name this process.
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Figure 3 shows a set-up used by a student to prepare dry chlorine gas in the laboratory.
Identify three mistakes in the set-up, and give a reason for each.
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When ethene gas is compressed at a high temperature, a solid is formed.
(a) Give the name of the solid. (b) Explain why it is not advisable to allow the solid to accumulate in the environment.
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(a)Polythene / Polyethene
(b)It is non-biodegradable, hence pollutes the environment.
30.0 cm3 of aqueous sodium hydroxide containing 8.0 g per litre of sodium hydroxide were completely neutralized by 0.294 g of a dibasic acid. Determine the relative formula mass of the dibasic acid. (Na = 23.0 ; 0 = 16.0; H 1.0)
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(a) State Graham’s law of diffusion
(b) Explain why a balloon filled with helium gas deflates faster than a balloon of the same size filled with argon gas.
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(a) Graham’s Law of diffusion
The rate of diffusion of a gas is inversely proportional to the square root of its density at constant temperature and pressure. (b)Helium is less dense than argon hence it diffuses out of the balloon faster than argon.
One of the allotrope s of sulphur is rhombic sulphur.
(a) Name the other allotrope of sulphur. (b) Draw a diagram to show the shape of the allotrope named in (a) above. (c) Write an equation for the reaction between concentrated sulphur(VI) acid and sulphur
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(a) When 0.048 g of magnesium was reacted with excess dilute hydrochloric acid at room temperature and pressure, 50 cm3 of hydrogen gas was collected. (Mg = 24.0; Molar gas volume = 24.0 dm3)
(i) Draw a diagram of the apparatus used to carry out the experiment described above.
(ii) Write the equation for the reaction. (iii) Calculate the volume of hydrogen gas produced. (iv) Calculate the volume of 0.1 M hydrochloric acid required to react with 0.048 g of magnesium.
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W is a colourless aqueous solution with the following properties:
(ii) Give the identity of W. (iii) Name the colourless solution formed in (II) and (III). (iv) Write an ionic equation for the reaction indicated in (V). (b) Element V conducts electricity and melts at 933K. When chlorine gas is passed over heated V, it forms a vapour that solidifies on cooling. The solid chloride dissolves in water to form an acidic solution. The chloride vapour has a relative molecular mass of 267 and contains 19.75% of V. At a higher temperature, it dissociates to a compound of relative molecular mass 133.5. When aqueous sodium hydroxide is added to the aqueous solution of the chloride, a white precipitate is formed which dissolves in excess alkali. (V = 27.0 ; CI = 35.5) (i) Determine the:
(iii) Write an equation for the reaction that form a white precipitate with sodium hydroxide.
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When an aqueous solution of compound X was mixed with a few drops of bromine water, the colour of the mixture remained yellow.
When another portion of solution X was reacted with acidified potassium dichromate(VI), the colour of the mixture changed from orange to green. (a) What conclusion can be made from the use of: (i) bromine water? (ii) acidified potassium dichromate(VI)? (b) Solution X was reacted with a piece of a metal and a colourless gas was produced. Describe a simple experiment to identify the gas.
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(a) What is meant by the term bleaching?
(b) Write the formula of the bleaching nent formed when chlorine gas reacts with aqueous sodium hydroxide. (c) State the role of chlorine in water treatment.
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January 2025
AuthorMaurice Atika is a teacher and a netprenuer. |
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