198 SMITH'S INTERMEDIATE CHEMISTRY 



ride ions. By making use of the fact that the chloride ion diffvses 

 more rapidly than the sodium ion (into a layer of pure water, for 

 example, carefully poured over the solution) we can bring about 

 a slight separation of the two ions, the water layer becoming 

 negatively charged and the solution positively. The passage of 

 the current does not cause ionization, it merely makes its existence 

 more obvious, effectually separating the ions by forcing them 

 to migrate in different directions towards the oppositely-charged 

 electrodes. 



Exercises. 1. Which are the anions and which the cations in 

 the substances whose formulae are given on p. 189? 



2. Using the models given in p. 182, make the ionic equations 

 representing the ionization of all the acids, bases, and salts, the 

 formulae of which are given on p. 170. 



3. Make an ionic equation (p. 185) for the displacement: 

 (a) of hydrogen from dilute hydrochloric acid by magnesium; 

 and (b) of copper from cupric sulphate solution by zinc. 



4. Rewrite the double decompositions on pp. 166-168 in full 

 ionic form. 



5. Why does a solution of 0.1 N hydrochloric acid conduct 

 the current nearly twice as well as a solution of 0.1 N sodium 

 hydroxide, and nearly four times as well as a solution of 0.1 N 

 sodium chloride? 



6. From the results given on p. 177, calculate the degree of 

 ionization of sodium chloride in a solution containing 1 gr. mol. 

 wt. NaCl to 1000 g. water (a) at the boiling-point, and (b) at 

 the freezing-point. 



7. From the results given on p. 177, calculate the degree of 

 ionization of potassium chloride in a solution containing 1 gr. 

 mol. wt. KC1 to 1000 g. water at 20. 



