THE RECOGNITION OF SUBSTANCES, II, ETC. 541 



Exercises. 1. Name some substances that have a metallic 

 luster, but are not metals or alloys. 



2. Name the metals whose salts with active acids will give : (a) 

 neutral aqueous solutions; (b) acid aqueous solutions. What 

 classes of salts will give alkaline solutions? 



3. Write full ionic equations for the chloride precipitations 

 mentioned in Group I. Why is silver chloride soluble in am- 

 monia? 



4. Write full ionic equations for the sulphide precipitations 

 mentioned in Group II. Which is more soluble in water, mer- 

 curic sulphide or cadmium sulphide? 



5. Write full ionic equations for the hydroxide precipitations 

 mentioned in Group Ilia. Which is the more soluble in water, 

 aluminium hydroxide or magnesium hydroxide? 



6. Show, by means of ionic equations, why it is possible to 

 prevent the precipitation of magnesium hydroxide when am- 

 monium hydroxide is added to a soluble magnesium salt, by 

 prior addition of ammonium chloride. 



7. Why is it not possible, in the same way, to prevent the 

 precipitation of magnesium hydroxide when sodium hydroxide 

 is added to a soluble magnesium salt, by prior addition of sodium 

 chloride? 



8. Write full ionic equations for the sulphide precipitations 

 mentioned in Group Illb. Which is the more soluble n water, 

 nickel sulphide or zinc sulphide? 



9. Write full ionic equations for the carbonate precipitations 

 mentioned in Group IV. 



10. Write full ionic equations for the reactions mentioned in 

 Group V. 



11. Give a precipitation test for the negative radical in each 

 of the following substances: sodium hydroxide, potassium car- 

 bonate, sodium sulphide, sodium phosphate. Write full ionic 

 equations in each case. 



