1918 

 CHEMISTRY 



Friday, June 21 2 p.m. Two hours 



Answer nine questions as indicated below. No extra credit will be given for more 

 than nine questions. > 



Attach to the answer, in each case, the number and letter used in the printed paper. p^ 



Part I 



{Answer all questions in this part. Each question counts 12.) 



1. Write equations for the following reactions, using formulas throughout. The 



equations must be correct in every particular. 



(a) Ammonium nitrate (heated) = 



{b) Ferric chloride + zinc = 



(c) Methane (marsh gas)+oxygen (ignited) = 



{d) Hydrogen sulphide+ silver nitrate = 



(e) Copper oxide (heated) + hydrogen = 



(/) Calcium oxide+sodium carbonate + water = 



2. How would you prove, by chemical means, the presence (a) of carbon mon- 



oxide if mixed with sulphur dioxide ? {b) of hydrogen if mixed with dry 

 air (if the amount of hydrogen is too small to make the mixture explosive) ? 

 (c) of gold in copper ? {d) of sulphuric acid in a solution of hydrochloric 

 acid? 



3. (a) What is the percentage of ammonia in cuprammonium sulphate, 



CuS04-4NH3-H20 ? (Atomic weights: Cu 64, S 32, 16, N 14, H 1.) 



(6) What weight of pure sodium bicarbonate, NaHCOa, must be treated with 

 excess of acid to produce 250 liters of carbon dioxide measured at 0° C. 

 and 1520 mm. pressure? (Atomic weights: Na 23, O 16, C 12, H 1. 

 One liter of carbon dioxide at 0° C. and 760 mm. weighs 1 .98 grams.) 



4. (o) Given the valence of A as three, derive the probable valences of B, C, and 



D from the following formulas: A2B3, B2C, B5D2. What would be the 

 formula of a compound of A with C ? 



{b) Prove that the law of definite proportions is a necessary consequence of 

 the atomic theory; 



5. Describe a method for the preparation of three of the following substances: 



(a) sodium, {b) nitric acid, (c) hydrogen sulphide, {d) calcium carbonate. 

 How would you separate the desired product, in each case, from the reaction 

 mixture ? 



30 (SEE NEXT PAGE) 



