3) Using concentrations of solutions in mol/dm3

• Acids and alkalis react together to form a neutral solution.
• Titration is an accurate technique that can be used to find out how much of an acid is needed to neutralise an alkali.
• When neutralisation takes place, the hydrogen ions (H+) from the acid join with the hydroxide ions (OH-) from the alkali to form water (neutral pH).
• H+(aq) + OH-(aq) → H2O(1)
• • You must use a suitable indicator in titrations.
• If you have a strong acid and strong alkali, you could use methyl orange or phenolphthalein.
• Hydrochloric acid, nitric acid and sulfuric acid are all strong acids.
• Aqueous sodium hydroxide and aqueous potassium hydroxide are strong alkalis
• • Titration can be used to find the concentration of an acid or alkali, providing the following are known:

  • the relative volumes of acid and alkali used
  • the concentration of the other acid or alkali.
• 1)Write down a balanced equation for the reaction to determine the ratio of moles of acid to alkali involved.

  2)Calculate the number of moles in the solution of known volume and concentration. You can work out the number of moles in the other solution from the balanced equation.

  3)Calculate the concentration of the other solution.