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ELECTROVALENT REACTIONS 589

being formed as rapidly as they are used up, so that for all

purposes the reaction has ceased.

practical

If one or both of the products of a reaction should be removed, the

reverse reaction would be impossible, and the original reaction would

go to completion. Inasmuch as chemical reactions between solutions

of electrolytes are really reactions between the ions,

the problem resolves

itself into that of removing one or more of the ions of the reaction

products. Ions may be removed from solution in the following ways:

1. By the formation of an insoluble substance.

a) By the formation of a precipitate. If ions combine to form an

insoluble solid, it is evident that they are thereby removed from

the solution.

h) By the formation of a gas. If ions combine to form an insoluble

gas, which bubbles out of the solution, it is evident that they

would likewise be removed from the solution.

2. By the formation of slightly ionized soluble substances.

a) By the formation of slightly ionized molecules. The formation of

slightly ionized molecules would certainly greatly reduce the

concentrations of the ions concerned in the solution, depending

upon the apparent degree of ionization of these molecules.

h) By the formation of complex ions from simpler ions, thus removing

the simpler ions from solution.

Additional applications of the theory of electrolytic dissociation

will be discussed in the next two Sections.

1. Define electrolyte.

STUDY QUESTIONS

2. What two types of phenomena does the theory of electrolytic dissociation

explain?

3. What types of compounds are electrolytes?

4. Outline briefly the main points of Arrhenius' theory of electrolytic dissociation.

5. How did Arrhenius explain the fact that solutions of some electrolytes conduct

the current better than solutions of other electrolytes?

6. What do solutions of all acids have in common?

7. What are the characteristic ions of bases?

8. Give four methods of removing ions from solution.

9. Why do reactions go to completion?

10. Differentiate between strong and weak electrolytes.

11. Define (o) acid, {b) base, (c) salt, {d) acid salt, (e) basic salt.

12. What is electrolysis?

13. What are the irregularities of solutions of electrolytes?

14. State Faraday's laws.

15. What are ions and how are ions formed?

16. What determines the charge on an ion?

17. Define (a) cathode, and {b) anode.

18. How would you define cations and anions?

19. Are metallic ions cations or anions?

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