Use the information in the table above to answer the questions that follow
a) i) Are the members in this group likely to be conductor or non – conductors? (1mk)
ii) Which element would have the lowest atomic number? Explain. (1mk)
b) The grid below represents part of the periodic table. Study it and answer the questions that follow. (The letters are not the actual symbols of the elements)
b) The grid above represents part of the periodic table. Study it and answer the questions that follow. (The letters are not the actual symbols of the elements)
i) Select the element in period three which has the shortest atomic radius. Give a reason for your answer. (2mks)
ii) Using dots (•) and crosses (x) to represent outermost electrons, draw a diagram to show the bonding in the compound formed when chlorine reacts with element X (1mk)
½mk @ x 2 = 1mk Penalize fully if dots or crosses alone are used
iii) When three liters of chlorine gas were completely reacted with element Y, 11.85g of the product were formed. Calculate the relative atomic mass of element Y. (3mks)(R.A.M of chlorine = 35.5, molar gas volume = 24 liters) 
Differentiate between empirical and molecular formula (2mks)
Empirical formula show the simplest whole number ration in which atoms combine to for a compound while molecular formula shows actual number of each kind of atoms present in a molecule of a compound.
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 mass of 2.5g of acid HX was dissolved in water and the resulting solution was diluted to a total of 250cm3, 15cm3 of the final solution was required to neutralize 25.0cm3 of 0.1M aqueous potassium hydroxide. Calculate the relative molecular mass of the acid (3mks)
a) How do their rate of diffusion compare? (2mks)
b) Determine the relative molecular mass of X given that the relative molecular mass of Y is 64 (1mk)
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.
ANSWERS
Distinguish between empirical and molecular formula of a compound.
ANSWERS
(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
ANSWERS
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)
ANSWERS
(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.
ANSWERS
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.
ANSWERS
20 cm3 of ethanoic acid was diluted to 400 cm3 of solution. Calculate the concentration of the solution in moles per litre. (C = 12.0 ; H = 1.0 ; 0 =16.0) (Density of ethanoic acid = 1.05 g/cm3)
ANSWERS
The empirical formula of lead(II) oxide was determined by passing excess dry hydrogen gas over 6.69g of heated lead(II) oxide.
(a) What was the purpose of using excess dry hydrogen gas? (b) The mass of lead was found to he 6.21g. Determine the empirical formula of the oxide. (Pb = 207.0 0 = 16.0)
ANSWERS
Use the information in the table below to answer the questions that follow. The letters do not represent the actual symbols of the elements.
(a) Give reasons why the melting point of:
(i) S is higher than that of R; (ii) V is lower than that of U. (b) How does the reactivity of W with Chlorine compare with that of R with chlorine? Explain. (c) Write an equation for the reaction between T and excess oxygen. (d) When 1.15g of R were reacted with water, 600cm3 of gas was produced. Determine the relative atomic mass of R. (Molar gas volume = 24 000 cm3). (e) Give one use of element V.
ANSWERS
(a) Explain the following observations:
(b) A sample of water is suspected to contain aluminium ions (AI3+) . Describe a laboratory experiment that can be carried out to show that AI3+ ions are present in the water sample. (3 marks) (c) In an experiment to determine the number of moles of water of crystallisation of a hydrated compound, Na2S04. X H2O, 5g of the compound were heated strongly to a constant mass.
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AuthorMaurice Atika is a teacher and a netprenuer. |
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