Chemistry Past Questions and Answers

(a) Give one example of a metal which:<br/>(i) can displace hydrogen from cold water<br/>(ii) at red-heat, reacts reversibly with steam<br/>(iii) does not react with dilute hydrochloric acid<br/> <br/>(b) When dry hydrogen was passed over lead (II) oxide, a greyish solid J was obtained.<br/>(i) Identify J<br/>(ii) What type of reaction was involved in the formation of J from lead (II) oxide?

(a)(i) Define entropy<br/>(ii) What term is used to describe a reaction in which heat is absorbed from the surrounding?<br/>(b) State two conditions that can lead to ineffective collisions during a chemical reaction.

(a)(i) List two reactants for the laboratory preparation of ammonia<br/>(ii) State three physical properties of ammonia<br/>(iii) Describe in outline, the manufacture of ammonia by the Haber process.<br/> <br/>(b) Write an equation in each case to show the:<br/>(i) reaction between ammonia gas and heated copper (II) oxide<br/>(ii) action of heat on ammonium trioxocarbonate (IV)<br/> <br/>(c)(i) Which industrial process is used for convey ammonia to trioxonitrate (V) acid?<br/>(ii) Give the reason why electropositive metals do not generally are off hydrogen with dilute trioxonitrate (V) acid<br/>(d) Give one example in each case, to show how trioxonitrate (V) acid reacts generally with: (i) bases (ii) non-metals.

(a)(i) State two general methods of preparing soluble salts.<br/>(ii) Mention three pieces of apparatus required for determining the solubility of a salt at a given temperature.<br/> <br/>(b) The solubilities of two salts represented as K and L were determined at various temperatures. The results are shown in the table below:<br/><table class='tbn'><tbody><tr><td> Temperature (\(^o\)C) </td><td> 0 </td><td> 20 </td><td> 40 </td><td> 60 </td><td> 80 </td><td> 90 </td></tr><tr><td> Solubility of K (mol. dm\(^{-3}\)) </td><td> 0.38 </td><td> 0.46 </td><td> 0.54 </td><td> 0.62 </td><td> 0.69 </td><td> 0.73 </td></tr><tr><td> Solubility of L (mol. dm\(^{-3}\)) </td><td> 0.12 </td><td> 0.34 </td><td> 0.64 </td><td> 1.08 </td><td> 1.64 </td><td> 2.00 </td></tr></tbody></table><br/><br/><br/> <br/>(i) Plot the solubility curves of K and L on the same graph. Use the curves to answer questions (ii) - (iv) below.<br/>(ii) What is the solubility of K at 50°C?<br/>(iii) At what temperature is the solubility of L equal to 1.0mol. dm\(^{-3}\)?<br/>(iv) Over what temperature range is K more soluble that L?<br/>(v) Given that the molar mass of L is 101g, determine whether a solution containing 3.4g of L per 250cm\(^3\) at 20°C is saturated or unsaturated.

(a)(i) What is meant by cracking of petroleum fractions?<br/>(ii) Write an equation for the laboratory preparation of ethene from ethanol.<br/>(iii) Give one chemical test to distinguish between ethane and ethene.<br/> <br/>(b)(i) Name the class of carbohydrates to which starch and cellulose belong.<br/>(ii) What process is used for isolating ethanol from the other products of fermentation of sugar?<br/>(iii) Name the organic product of the reaction between ethanol and sodium<br/>(iv). Write the structural formula of 2-chloroethanol.<br/> <br/>(c) State the reason why:<br/>(i) benzene produces more soot than ethene on burning in excess air;<br/>(ii) ethanoic acid has a higher boiling point than methanoic acid;<br/>(iii) sodium chloride is used during the manufacture of soap.<br/>(d) Give one use of: (i) ethyne (ii) coal (iii) carbon black