CARBON AND THE OXIDES OF CARBON 341 



Exercises. 1. (a) What physical property of graphite enables 

 it to cover the surface of a stove so effectively? (b) How does 

 " polishing " with a brush contribute to the result? (c) Why not 

 use paint on a stove? (d) Explain why graphite can be used as a 

 lubricant. 



2. If a metal formed the positive electrode (anode) in electrolyz- 

 ing sodium chloride solution, what chemical change might it 

 undergo (p. 54), and which metals would be least rapidly attacked? 

 What objection is there to using the latter metals in practice? 



3. When one cubic meter of oxygen acts upon carbon, what 

 volumes (at the same temperature and pressure): (a) of carbon 

 dioxide; (b) of carbon monoxide can be obtained? 



4. Make the equation: (a) for the formation of methane by 

 union of carbon and hydrogen; (b) for the reduction of stannic 

 oxide (Sn0 2 ) by carbon. 



5. Make equations for: (a) the action of sulphuric acid upon 

 calcium carbonate; (b) carbon dioxide on sodium hydroxide solu- 

 tion (p. 336) ; (c) the burning of aluminium in carbon dioxide. 



6. From the fact that the molecular weight of carbon dioxide is 

 44, how do we infer that it is one-half heavier than air? 



7. Why does soda water remain quiescent in the closed bottle, 

 and why does it effervesce when the bottle is opened? 



8. Rewrite the equations on p. 336 in full ionic form. 



9. Name the variety of chemical change (p. 132) to which 

 belongs the reaction hown in each equation in this chapter. 



10. Assuming that air contains oxygen and nitrogen in the pro- 

 portion of 1 : 4 by volume, what are the theoretical proportions of 

 carbon monoxide and nitrogen in producer gas? 



11. (a) What volume of water gas is produced from each liter of 

 steam, and (b) what is the proportion of the component gases in 

 the product? (c) What impurities should you expect to find in 

 water gas? (d) How should you attempt to separate the com- 

 ponents of water gas? 



