4 VETEEINAEY STATE BOAED 



due to the loss of its water of crystallization. Example: crystal- 

 line sodium sulphate, exposed to the air, becomes a white powder. 

 A deliquescent substance is one which can be converted from a 

 soUd salt into a liquid form by the absorption of moisture from 

 the air. Example: calcium chloride left in an open vessel for a 

 few days will become wet and in time will even liquefy. 



Define acid salt, amalgam, molecular repulsion, neutralization. 



An acid salt is one in which only part of the hydrogen of an 

 acid is replaced by a metal or basic radical. Example : NaHSO^. 



An amalgam is an aUoy containing mercury, as tin and mercury. 



Molecular repulsion is the term applied to the tendency of 

 molecules to separate. According to the theory of the constitution 

 of matter, the molecules of every mass are in ceaseless motion, 

 hitting and rebounding from one another. In gaseous masses, the 

 molecules move without restraint; hence gases always tend to 

 expand. 



Neutralization is the term applied to the interaction between 

 acids and bases with the result that both acid and basic properties 

 disappear, i.e., are neutralized. It consists in the union of the 

 hydrogen ion of an acid with the hydroxyl ion of a base to form 

 water. 



Define valence and write formulas of four compounds containing ele- 

 ments having different valences, indicating the valence in 

 each case. 



Valence is the definite capacity which every elementary atom 

 has for uniting with other atoms. Hydrogen is taken as the standard 

 and its valency is assumed to be unity. In HCl, CI is univalent 

 because it combines with one atom of H; in H^O, is bivalent; 

 in NH3, N is trivalent ; in CH^, C is quadrivalent. 



Define monad, diad, triad, tetrad, pentad. Give an example of each. 



Monad is an element having a valency of one ; diad, a valency of 

 two ; triad, three ; tetrad, four ; pentad, five. 



Examples: see preceding answer; pentad, phosphorus as in 

 PCI5. 



Define monobasic acid, dibasic acid, tribasic acid. Give an example of 

 each. 

 A monobasic acid is one containing in its molecule one replace- 

 able atom of hydrogen, as nitric acid, HNO3. 



A dibasic acid is one having two replaceable atoms of hydrogen 

 in its molecule, as sulphuric acid, H^SO^. 



