QUESTIONS ON CHAPTERS XVI.-XVIII. 



113 



87. Five samples of a certain substance were strongly heated until no 

 further change in weight occurred, with the following results : 



What conclusions can you draw from the above data ? Name two 

 substances which might be used in a similar manner to support your main 

 conclusion. 



88. What do you mean by the term solubility ? The solubility of a 

 certain salt at various temperatures is given by the following table : 



If 250 gm. of water saturated with the salt at 55 C. be allowed to cool 

 to 20 C., what weight of salt will crystallise out ? 



89. Describe in detail the method of finding the solubility of nitre at 

 60 C. The following table gives the solubility of nitre in 100 grams of 

 water at various temperatures : 



10 C. - - - - 19-1 grams. 



SOC. - - - - 43-2 



40 C. - - - - 62-3 



50 C. - - - - 84-1 



70 C. - - - - 138-5 



Draw a graph, and from it calculate what weight of solution at 60 C. 

 will contain 5 Ib. of nitre. 



J.o.s. 



