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1920 

 CHEMISTRY 



Friday, June 25 2 p.m. Two hours 



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

 than nine questions. 



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



Part I 

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



1. Describe a method for the laboratory preparation of the following substances: 



(a) sodium chloride, {h) calcium carbonate, (c) nitric oxide. What 

 property has sodiimi chloride which makes it possible to separate it? 

 calcium carbonate ? nitric oxide ? 



2. Illustrate by equations the action of dilute sulphuric acid on (a) zinc, {b) cal- 



cium oxide, (c) ammonium hydroxide, {d) sodium carbonate, {e) ferrous 

 sulphide, (/) barium chloride. Name the type of reaction which occurs in 

 each case. Formulas must be used throughout and the equations properly 

 balanced to receive credit. 



3. Describe an experiment illustrating the quantitative character of chemical 



action, including apparatus, method, and precautions. Show how the 

 data found in the experiment warrant the conclusion reached The data 

 may be represented by letters. 



4. If 540 grams of silver react with an excess of concentrated sulphuric acid 



according to the equation 2 Ag+2 H2S04 = Ag2S04+2 H2O+SO2, what 

 weight of silver sulphate, and what volume of sulphur dioxide measured 

 under standard conditions of temperature and pressure, will be formed? 

 (Ag 108, 8 32,016, HI.) 



Note. — One liter of sulphur dioxide at 0° C. and 760 mm. weighs 2.9 grams. 



5. (c) Which contains the more energy under the same conditions of tempera- 



ture and pressure, a mixture of 1 gram of hydrogen and 8 grams of 

 oxygen or 9 grams of water ? Give the reason for your conclusion. 



{h) Name two elements having more than one valence. Illustrate each of 

 the valences of these elements by constructing a formula containing 

 also one element of constant valence. Write above the symbol of 

 each element, in each formula, its valence. 



(THIS EXAMINATION IS CONTINUED ON PAGE 2) 

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