IN POPULAR CHEMISTRY. 73 



The O contained in the air absorbed by the H 2 O oxidizes 

 the organic substances, which are the most dangerous impuri- 

 ties. 



14:. WJiatis the action of potassium, permanganate as 

 a disinfectant ? 



It gives up its O to oxidize the organic impurities. 



15. What weight of II can be obtained from a liter of 

 water ? 



The weight of a liter of water under standard conditions is 

 1,000 grams. Of this is H. Hence, the required weight is 

 grams. 



16. Hoiv much Zn must be employed to obtain 1OO 

 grams of H from H<>SO ? 



The reaction is 



Zn + H 8 SO 4 = ZnSO 4 + 2H. 

 Hence, 2H : Zn : : 100 : x. 



2 : 65 : : 100 : x. 

 x = 3,250 grams. 



17. A liter of H under standard conditions weighs 

 O.O896 grant. What volume of Hat 1O C. and 738 mm. 

 can be obtained from H^SO^ by the action of 8 Jcilos of 



Zn? 



Zn + H 2 SO 4 = ZnSO 4 + 2H. 



Zn : 2H : : 8,000 : x in grams. 

 65 : 2 : : 8,000 : x. 



x = 246.15 grams. 



The number of liters under standard conditions is 

 246.15 

 .0896 ' 



At 10 C. and 738 mm., the volume is 

 _ 246.15 283 760 

 " 70896" X 273 X 738' 

 V = 2932.7 liters. 



IS. How much KCIO 3 would be required to evolve suffi- 

 cient O to burn the H produced by the decomposition of 2 

 grams of H Z O? 



