124 



(b) sugar, or (c) sugar and grease together, or (d) varnish, how 

 should you proceed in each case to remove the spot? 



3. If chalk (5 g.) and potassium chlorate (5 g.) were mixed, how 

 should you separate them (p. 13)? Explain how you could secure 

 each substance. 



4. Could you make (a) a concentrated, (b) a saturated solution 

 of chalk in water (p. 111)? Of alcohol in water? 



5. If you saturated 200 c.c. of water at 70 with (a) salt, or 

 (b) potassium nitrate, and then cooled the clear liquid to 20, 

 what weight of the solid substance would separate out in each case 

 (p. 113)? 



6. To make as concentrated a solution of lime water as possible, 

 should you use hot water or cold (p. 113)? 



7. Explain why boiled water has a slightly different taste from 

 tan-water that has not been boiled (p. 66). 



(s^ If 100 g. of a non-volatile substance, dissolved in 1000 g. 

 of benzene (C 6 H 6 ), lower the vapor pressure from 74.8 to 68.0 

 mm., what is the molecular weight of the substance (pp. 117-8)? 



9. Explain why potassium carbonate becomes wet, and finally 

 dissolves, when exposed to moist air. How must calcium chloride 

 be preserved from becoming moist? 



10. If 52 g. of a substance dissolved in 1000 g. of water gives a 

 solution boiling at 100.26, what is the molecular weight of the 

 substance (p. 119)? 



11. If 68.5 g. of a substance, dissolved in 500 g. of water 

 gives a solution freezing at 1.86, what is the molecular weight 

 of the substance (p. 119)? 



12. How much glycerine (C 3 H 8 3 ) could you dissolve in 1000 g 

 of water, and still be able to freeze the water with ice and salt 

 (p. 119)? 



13. Explain why a sodium acetate hot-water bottle can be used 

 over and over again. What is the source of the heat it gives out 

 each time it is used? 



