206 ELEMENTARY GENERAL SCIENCE CH. xm 



and the group of elements, S0 4 , reacts with water as described in 

 the case of the electrolysis of copper sulphate. The final result 

 is that hydrogen is evolved at the kathode and oxygen at the 

 anode. 



QUESTIONS ox CHAPTER XIII. 



1. Describe fully what takes place when each of the following 

 liquids is included in a circuit round which a strong electric 

 current is circulating : 



(a) Liquid mercury. 



(b) Petroleum. 



(c) Acidulated water. 



2. What means would you adopt to recognise the passage of an 

 electric current through a wire ? 



3. What do you understand by electrolysis ? Give an account of 

 the electrolysis of water. 



4. Explain the terms : electrolyte, anode, kathode, ion. 



5. What happens precisely when an electric current is passed 

 through a solution of copper sulphate in water. What appears at 

 the anode, and how do you account for its appearance ? 



6. Explain by the aid of chemical symbols the various chemical 

 changes which take place during the passage of the electric current 

 in the last question. 



7. Write a short essay on the electrolysis of a solution of sodium 

 sulphate. 



8. Clearly explain the appearance of hydrogen at the kathode 

 when an electric current is passed through a solution of Glauber's 

 salt. 



9. After the passage of an electric current through a solution 

 of sodium sulphate, the liquid round the anode is found to turn 

 a blue litmus paper red. Explain this. 



