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O LevelChemistryCambridgeRevision Notes3. Stoichiometry3.3 The Mole & the Avogadro ConstantTitration Calculations

Titration Calculations (Cambridge O Level Chemistry)

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Titration Calculations

  • Titrations are a method of analysing the concentration of solutions
  • Acid-base titrations are one of the most important kinds of titrations
  • They can determine exactly how much alkali is needed to neutralise a quantity of acid – and vice versa
  • You may be asked to calculate the moles present in a given amount, the concentration or volume required to neutralise an acid or a base
  • Once a titration is completed and the average titre has been calculated, you can now proceed to calculate the unknown variable using the formula triangle as shown below

Concentration moles formula triangle, downloadable IB Chemistry revision notes

Formula triangle showing the relationship between concentration, number of moles and volume of liquid

Worked example

A solution of 25.0 cm3 of hydrochloric acid was titrated against a solution of 0.100 mol/dm3 NaOH and 12.1 cm3 were required for complete reaction. Determine the concentration of the acid.

Answer

Step 1: Write the equation for the reaction:

HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)

Step 2: Calculate the number of moles of the NaOH

Moles = (volume ÷ 1000) x concentration

Moles of NaOH = 0.012 dm3 x 0.100 mol/dm3 = 1.21 x 10-3 mol

Step 3: Deduce the number of moles of the acid

Since the acid reacts in a 1:1 ratio with the alkali,  the number of moles of HCl is also 1.21 x 10-3 mol

This is present in 25.0 cm3 of the solution (25.0 cm3 = 0.025 dm3)

Step 4: Find the concentration of the acid

Concentration = moles ÷ volume (dm3)

Concentration of HCl =1.21 x 10-3 mol  ÷ 0.025 dm3 = 0.0484 mol/dm3

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    Caroline

    Author: Caroline

    Expertise: Physics Lead

    Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.