I3 2 ANSWERS TO PRACTICAL QUESTIONS 



Find (i) how much S there is in the given weight of 

 iron pyrites ; (2) how much ferrous sulphate could be 

 made from that amount of S, if it were all oxidized, 

 (i). 230 tons x .375 = 86.25 tons (S). 



(2). S : FeSO 4 , 7H a O : : 86.25 tons : x. 

 32 : 278 : : 86.25 tons : x. 



32 x = 23977.5 tons. 



x = 749.296 tons (FeSO, 7H a O). 



50. Required $w tons of soda crystals ; what will be the 

 weight of salt and pure sulphuric acid needed'} 



Find (i) how much Na there is in 500 tons of " soda," 

 and (2) how much NaCl would be needed to furnish that 

 amount of the metal in case all were utilized. 



(i). Na a : Na a CO 3 ,ioH a O : : x : 500 tons. 

 46 : 286 : : x : 500 tons. 



286 x = 23,000 tons. 



x = 80.42- tons (Na). 



( 2 )- sis f an y amount of NaCl is Na ; hence, to furnish 80.42 tons of Na 

 would require || x 80.42 tons = 204.546 tons (NaCl). 



(3). By comparing the atomic weights of the substances it will be seen 

 that for 46 parts of Na there must be 98 of pure H a SO.. ff x 204.546 tons = 

 435.771 tons (H,SO). 



51. Describe the uses of lime in agriculture. 



(See Key, page 51, Question 12.) 



52. How many tons of oil of vitriol, containing 70 per 

 cent, of pure acid (H 2 SO 4 ), can be prepared from 250 tons 

 of iron pyrites, co?itaining 42 per cent, of sulphur 1 



(i). (See Question 49.) 250 tons x .42 = 105 tons (S). 



(2). S : H 2 SO 4 : : 105 tons : x. 

 32 : 98 : : 105 tons : x. 

 32 x = 10290 tons. 



x = 321.56 tons (H 2 SO). 



(3). If 321.56 tons (H 2 SO) is 70 % of the given oil of vitriol, the entire 

 amount would be 321.56 tons x Vr = 459-28 tons (oil of vitriol). 



