acids, bases + salts (2)

acids, bases + salts (2)

1. neutralisation reactions

   • when the H+(aq) ions from an acid react with the OH-(aq) ions from an alkali, a neutralisation reaction occurs to form water
   • e.g H+(aq) + OH-(aq) -> H20(l)

2. acids

   • when acids dissolve in water they produce aqueous hydrogen ions, H+ (aq)
   • e.g. hydrocholric acid

3. alkalis

   • when alkalis dissolve in water they produce aqueous hydroxide ions, OH- (aq)
   • e.g sodium hydroxide

4. state symbols

   • (s) - solid
   • (l) - liquid
   • (g) - gas
   • (aq) - aqueous (dissolves in water)

5. making soluble salts

   • when acids react with bases, a salt and water are made:
     • acid + metal oxide -> salt + water
     • acid + metal hydroxide -> salt + water
   • reactive metals
     • acids will react with reactive metals, such as magnesium and zinc, to make a salt and hydrogen:
       • acid + metal -> salt + hydrogen
       • the hydrogen causes bubbling during the reaction, this can be detected using a lighted splint

6. naming salts

   • the name of the salt in a neutralisation reaction can be predicted
     • if the first part of the name is 'ammonium' then the base used is ammonia, otherwise it's the name of the metal in the base
     • the second part of the name comes from the base used:
       • chloride - if hydrochloric acid is used
       • nitrate - if nitric acid is used
       • sulfate - of sulfuric acid is used

7. making insoluble salts

   • insoluble salts DO NOT dissolve in water
   • can be made by mixing appropriate solutions of ions together
   • e.g.silver chloride is insoluble, you need soluble silver salt and a soluble chloride salt to make it
     • silver nitrate and sodium chloride are both soluble, when you mix their solutions together you make:
       • soluble sodium nitrate
       • insoluble silver chloride
     • the silver chloride appears in tiny particles suspended in the reaction mixture, it forms a precipitate
       • the precipitate can be filtered, washed with water on the filter paper, and then dried in an oven
   • if you want to make an insoluble salt XY, mixing X nitrate with sodium Y will always work
     • in the e.g. X is silver and Y is chloride

8. using precipitation reactions

   • they can be used to remove unwanted ions in solutions, this is a useful way for treating drinking water and waste water