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1920 

 Comprehensive Examination 



CHEMISTRY 



Wednesday, June 23 2-5 p.m. 



Answer ten questions as indicated below, 



Niunber and letter your answers to correspond to the questions selected. 



Part I 

 (Answer all questions in JPart I.) 



1. Classify the following compounds into (o) acids, {h) bases, (c) salts, {d) acid 



anhyrides, {e) substances belonging to none of the foregoing four classifica- 

 tions: sulphur dioxide, calcium oxide, ammonium carbonate, iron sulphide, 

 sodium hydroxide, phosphorus pentoxide, barium chloride, hydrogen 

 sulphide. 



2. Write equations for the following reactions, using formulas throughout. 



The equations must be properly balanced to receive credit. Indicate by 

 reversed arrows those reactions which do not go almost to completion. 



a) Silver+hot concentrated sulphuric acid= (sulphur dioxide is formed). 



h) Ammonium sulphate heated with sodium chloride = 



c) Carbon disulphide burned in an excess of ox}'gcn = 



d) Sodium chloride, carbon dioxide, ammonia, and water = 



e) Hydrogen+ nitrogen, heated with a catalyzer = 



3. Baking powder can be made by mixing baking soda, NaHCOs, and cream of 



tartar, HKC4H4O6. These substances react according to the following 

 equation: 



NaHC03+HKC4H406 = H20+C02+NaKC4H406 



a) How much cream of tartar should be mixed with one kilogram of baking 



soda so that neither ingredient will be in excess ? 

 h) WTiat volume of carbon dioxide at 0° C. and 760 mm. may be obtained 



from the baking powder thus made ? (K 39, Na 23, O 16, C 12, H 1.) 

 Note. — One liter of CO2 at 0° C and 760 mm. weighs 1.98 grams. 



4. a) What is the relation between volume and pressure of a gas when the 



temperature is constant? between volume and temperature when the 

 pressure is constant ? between temperature and pressure when volume 

 is constant ? 



h) From the standpoint of the molecular hypothesis explain the fact that 

 (1) 40 gallons of o.xygen may be forced into a small steel cylinder, (2) gas 

 escapes from a glass of soda water, (3) chlorine gas, although heavier 

 than air, escapes from an upright vessel. 



5. Tell how you would determine experimentally (a) either the equivalent of 



some element or the molecular weight of some gas; {b) either the percentage 

 of carbon dioxide in exhaled air or of oxygen in ordinary air. Indicate 

 the method of computing the result in each case. 



(THIS EXAMINATION IS CONTINUED ON PAGE 2) 



