Titrations

• Procedure for carrying out a titration


  1. Transfer 25 cm³ of sodium hydroxide solution into a conical flask

  2. Add 5 drops of indicator (e.g. methyl orange) to the alkali

  3. Place conical flask on a white tile

  4. Fill a burette with sulfuric acid

  5. Add acid to the alkali until the solution is neutral (colour change from yellow to permanently red)

  6. Read the volume of acid added from the burette (at the bottom of the meniscus)

  7. Repeat the titration until two readings are within 0.1 cm³

  8. Take the mean of the two readings
• Titration


  A procedure to determine the concentration of an acid or alkali by neutralization
• Neutralization reaction


  Reaction between an acid and an alkali to form a salt and water
• Indicator


  A substance that changes colour at a specific pH, used to determine when neutralization is complete
• Meniscus


  The curved upper surface of a liquid in a container, caused by surface tension
• It is important to read the burette at the bottom of the meniscus
• Carrying out a titration is a required practical for students studying triple chemistry
• Titration questions are highly likely to appear in the exam
• Concentration


  Moles per decimeter cubed
• Concentration


  Grams per decimeter cubed
• Titration calculation


  1. Convert volumes to decimeters cubed

  2. Calculate moles of one solution

  3. Use mole ratio to calculate moles of other solution

  4. Divide moles by volume to get concentration in moles per decimeter cubed

  5. Multiply moles per decimeter cubed by relative formula mass to get concentration in grams per decimeter cubed
• Titration


  • Used to determine the concentration of an acid or alkali
• Solving sample question


  1. Convert volumes to decimeters cubed

  2. Calculate moles of sodium hydroxide

  3. Use mole ratio to calculate moles of hydrochloric acid

  4. Divide moles of hydrochloric acid by volume to get concentration in moles per decimeter cubed

  5. Multiply moles per decimeter cubed by relative formula mass to get concentration in grams per decimeter cubed
• Solving practice question


  1. Convert volumes to decimeters cubed

  2. Calculate moles of calcium hydroxide

  3. Use mole ratio to calculate moles of sulfuric acid

  4. Divide moles of sulfuric acid by volume to get concentration in moles per decimeter cubed

  5. Multiply moles per decimeter cubed by relative formula mass to get concentration in grams per decimeter cubed
• Determining the concentration of an acid or alkali


  1. Write C=, N=, V= for acid and alkali

  2. Fill in known information

  3. Calculate moles of one reactant

  4. Use mole ratio to calculate moles of other reactant

  5. Calculate concentration in mol/dm³

  6. Calculate concentration in g/dm³
• Concentration


  Moles per decimeter cubed
• Concentration


  Grams per decimeter cubed
• This is for A-Level Chemistry higher only
• Sample question: 20 cm³ hydrochloric acid neutralized 25 cm³ calcium hydroxide (0.1 mol/dm³)


  1. Write C=, N=, V= for acid and alkali

  2. Calculate moles of calcium hydroxide

  3. Use mole ratio to calculate moles of hydrochloric acid

  4. Calculate concentration of hydrochloric acid in mol/dm³

  5. Calculate concentration of hydrochloric acid in g/dm³
• Practice question: 24 cm³ sulfuric acid neutralized 25 cm³ sodium hydroxide (0.1 mol/dm³)


  1. Write C=, N=, V= for acid and alkali

  2. Calculate moles of sodium hydroxide

  3. Use mole ratio to calculate moles of sulfuric acid

  4. Calculate concentration of sulfuric acid in mol/dm³

  5. Calculate concentration of sulfuric acid in g/dm³
• More questions available in the revision workbook