CHEMICAL NOMENCLATURE 277 



QUESTIONS ON CHAPTER XIX. 



1. What do you mean by the terms "atom" and "molecule?" 

 Carefully point out the difference between them. 



2. What is Avogadro's Law ? Indicate the use of this law in the 

 determination of molecular formulae. 



3. What is meant by " atomic weight" ? How does it differ from 

 " equivalent weight " ? Under what circumstances are they equal ? 



4. How would you endeavour to find the equivalent weight of a 

 metal soluble in sulphuric acid ? 



5. By what experiments and reasoning would you show that 

 hydrochloric acid gas should be represented by the formula HC1 ? 



6. What is "valency"? Give examples of elements possessing 

 different valencies. 



7. What is a chemical equation? Write down the equations 

 representing the changes of any three chemical operations you have 

 seen, and give in words the exact meaning of the equation. 



8. Write in words the exact meaning of the equation 2KC10 3 

 2KC1 + 30 2 . From this equation calculate the weight of oxygen 

 obtainable from 100 grams of potassium chlorate. 



9. Explain how the measurement of the density of a gas leads to 

 the determination of its molecular weight. State in words the law 

 upon which this determination is based. 



10. Explain clearly why we represent the molecule of water by 

 the formula H 2 O. 



11. " The molecule of hydrogen must contain at least two atoms." 

 Justify this statement. 



12. Sulphuretted hydrogen may be proved experimentally to con- 

 tain its own volume of hydrogen. Describe the experiment, and say 

 what it proves regarding the molecule of sulphuretted hydrogen. 



