Acids (Unit 1)

Acids (Unit 1)

1. The pH scale measures how acidic or alkaline a substance it is.

   • A pH of 7 is neutral
   • A pH greater than 7 are alkaline (basic)
     • Alkalis are bases that are soluble in water.
       • All alkalis are bases but not all bases are alkalis.
     • The higher the pH, the stronger the alkaline
   • A pH lower than 7 are acidic
     • The lower the pH, the stronger the acid
   • If a universal indicator is added to the solution, it changes colour to show the pH of the solution.

2. Bases and Alkalis

   • A base is a substance that neutralises an acid
   • Bases such as metal oxides and metal hydroxides react with acids to form neutral products
   • Examples of bases:
     • Copper Oxide
     • Zinc Hydroxide
   • Bases that are also soluble in water are called alkalis
   • Examples of alkalis:
     • Sodium Hydroxide
     • Potassium Hydroxide
   • All alkalis are bases

3. Alkali + Acid = pH of mixture rises

   • the alkali reacts with it forming neutral products

4. Acid + Alkali = the pH to fall

   • the alkali is removed by the reaction with the acid
     • when acidity or alkalinity is removed it is called NEUTRALISATION
       • a neutralisation always produces salt and water (nothing else)

5. Acid + base = salt + water

   • If the acid is hydrochloric acid,
     • the salt will be a chloride
     • Acid: hydrochloric acid
       • + Base: copper oxide
         • = Salt+Water: copper chloride+ water
   • If the acid is nitric acid,
     • the salt will be a nitrate
     • Acid: nitric acid
       • + Base: calcium hydroxide
         • = Salt+water: calcium nitrate + water
   • If the acid is sulfuric acid,
     • the salt will be a sulfate
     • Acid: sulfuric acid
       • + Base: sodium hydroxide
         • = Salt+water: sodium sulfate + water
     • Sufuric acid is used to clean metal surfaces before they're painted. It's also an important starting material in the production of fertilisers and is used in car batteries.

6. Examples of commonly used Acids and Alkalis

   • The pH scale using common everyday items

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