GROUP C 

 Answer one question from this group 



6. (a) A gaseous compound contains 85 . 71 per cent carbon, and 14 . 29 per cent 



hydrogen, and has a specific gravity (specific gravity of oxygen = 16) of 

 35; what is its formula? H = i, C = i2. 



(b) State and explain on the basis of the hypothesis of electrolytic disso- 

 ciation, what happens when a current of electricity is passed through an 

 aqueous solution of sodium chloride. 



7. Answer (a), and either (b) or (c), but not both. 



(a) Hydrogen sulphide combines with an excess of oxygen to form sulphur 

 dioxide and water vapor. What are the relations by volume between the 

 hydrogen sulphide, the oxygen, the sulphur dioxide, and the water vapor ? 

 State the hypothesis upon which your conclusion is based. 



(b) Describe an experimental mode of demonstrating that aluminium is 

 trivalent, the atomic weight of the element being assumed to be known. 



(c) Describe experiments which you could make to demonstrate the law of 

 definite proportions. State the law. 



GROUP D 

 Answer two questions from this group 



8. (a) Give the symbols and names of 16 common elements, writing them in 



groups according to the periodic classification. 



(b) (i) Describe briefly the mode of extracting the metal from one of 

 the important ores of aluminium or of zinc. 



(2) Name two practical uses to which this metal is put, and state what 

 property renders it particularly suited to each purpose named. 



9. (a) Give the chemical name, formula, color, and one important use of any 



five of the following substances: corrosive sublimate, galena, limestone, 

 blue vitriol, iron pyrites, magnetite, saltpeter, hypo, marsh gas. 



(b) Name three of the rare and inert gases and state where they are found. 



(c) What peculiar chemical property is shown conspicuously by radium ? 



10. (a) Name the raw materials from which two of the following substances 



are made, and explain one commercial method of manufacturing each 

 of the three: bleaching powder, soda, sulphuric acid, alcohol, kerosene. 



(b) Answer any one of the following: 



(1) Mention the three essential elements which plants obtain from the 

 mineral constituents of the soil and give examples of fertilizers 

 which furnish them. 



(2) Describe an experiment to show that electricity can be generated 

 as a result of chemical action. 



(3) In a photographic dry plate, what is the substance sensitive to light, 

 what function does the developer perform, and what is meant by 

 "fixing"? , 9 



