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Chemistry · Topic

Acids, bases, salts and titration calculations

Convert cm³ to dm³ by dividing by 1000 before multiplying by concentration.

1 original question in the bank, worth 3 marks · still building (1 more to reach the floor)

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Calculate3 marksIGCSE

25.0 cm³ of 0.100 mol/dm³ sodium hydroxide solution is exactly neutralised by 20.0 cm³ of hydrochloric acid. Calculate the concentration of the hydrochloric acid in mol/dm³.

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Answer: 0.125 mol/dm³

  1. Moles of NaOH = 0.100 × (25.0 ÷ 1000) = 0.0025 mol
  2. NaOH and HCl react 1:1, so moles of HCl = 0.0025 mol
  3. Concentration = 0.0025 ÷ (20.0 ÷ 1000) = 0.125 mol/dm³

Examiner technique: Two conversions to dm³, one ratio, one division. Write the volume conversion as its own step; it is the step learners skip and markers reward.