Chemistry Past Questions and Answers

(a) State the following laws of chemical combination: (i) Law of constant composition (ii) Law of multiple' proportion.<br/>(b) Copper reacts with oxygen to form two oxides X and Y. On analysis, 1.535 g of X yielded 1.365 g copper and 1.450 g of Y yielded 1.160 g of cooper.<br/>i) Determine the chemical formula of X and Y.<br/>(ii) Calculate the mass of copper which can react with 0.500 g of oxygen to yield I. X II. Y.<br/>(iii) Which of the laws of chemical combination is illustrated by the result in (b)(i) above. [ = 16, Cu = 63.51]<br/> <br/>(c) Write the structure of the product responsible for the observation in each of the following reactions:<br/>(i) A mixture of butanoic acid and ethanol warmed in the presence of concentrated H\(_2\)SO\(_4\) gives off a fragrant odour.<br/>(ii) Sodium dissolves in propan-2-ol with effervescence to give a solution which on evaporation to dryness leaves a white precipitate.<br/> <br/>(d) Consider the compound CH\(_3\)CH\(_2\)COOCH\(_2\)CH\(_3\).<br/>(i) Name the compound (ii) Write the structural formula of the compound (iii) State the reagents and conditions for the formation of the compound.

(a)(i) Draw and label a diagram to illustrate the preparation and collection of dry chlorine gas in the laboratory.<br/>(ii) List two uses of chlorine.<br/> <br/>(b)(i) Explain why river water flowing through an industrial town may be unsafe for drinking.<br/>(ii) State the use of each of the following substances in water treatment: I. Sand, II. Chlorine, III. Calcium oxide, IV. Alum<br/> <br/>(c)Consider the reaction represented by the following equation:<br/>2Na\(_2\)CI\(_{(s)}\) + H\(_2\)SO\(_{4(aq)}\) \(\to\) Na\(_2\)SO\(_{4(aq)}\) + 2HCI\(_{(g)}\)<br/>Calculate the volume of HCI gas that can be obtained at s.t.p. from 5.85 g of sodium chloride. [H = 1, Na = 23, CI = 35.5, Molar volume a 22.4 dm\(^3\) at s.t.p]<br/>(d) Give one example in each case of a (i) metal that is a liquid at room temperature. (ii) non-metal that is a iiquid at room temperature, (iii) gas at room temperature that is monatomic.<br/>(e) State two differences between metals and nom metals with respect to their: (i) physical properties; (ii) chemical properties.

When sodium atom form the ion Na<sup style='font-size: smaller;'>+</sup>,

Which of the following statements about rare gases are correct?

Which of the following properties is characteristic of the halogens?