18. (b) (i) Which compound should be heated with soda lime to obtain ethane gas in the laboratory?   19. (ii) Write the equation for the reaction in 2(b) (i) above.   20. (iii) Write a balanced equation for the complete combustion of ethane.   21. (iv) Name a solid which can be used instead of concentrated sulphuric acid to prepare ethylene by the dehydration of ethanol.   22. (v) Name a reagent which can be used to distinguish between ethane and ethene.   23. (vi) Ethylene forms an addition product with chlorine. Name this addition product and write its structural formula.