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Class 10 · English Medium · Pearson Edexcel · Chemistry

Quantities and chemical calculations

Use a titration equation to calculate an unknown concentration.

Original Kidemy further-topic investigation. This optional lesson is shared by related upper pathways; select suitable depth with a teacher. It does not certify complete grade or board coverage.

Learn the idea

A titre is the delivered volume used in the calculation. Convert it to dm³ when concentration is mol/dm³. The stoichiometric ratio comes from a balanced equation; equal volumes do not imply equal concentrations for every reaction.

Worked example

H2SO4+2NaOH→Na2SO4+2H2O. A 25.0cm³ acid sample reacts with 20.0cm³ of 0.100 mol/dm³ NaOH. Base amount0.00200 mol, acid0.00100 mol, so acid concentration0.0400 mol/dm³.

  1. Balance the equation.
  2. Convert volume and use mole ratio.
  3. Check units and measurement limits.

Your written practice

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0.03

Divide by 1000.

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0.008

n=cV.

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2

The coefficient ratio is 1:2.

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Show model answer and explanation

Base0.003 mol; acid0.0015 mol; concentration0.0015/0.025=0.06 mol/dm³.

Use the2:1 ratio and volume conversion.

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Show model answer and explanation

An overshoot is a procedural error and should be recorded and handled by a stated rule.

Explain consistency and transparent exclusions.

Apply the idea

Solve a fictional titration on paper and explain the ratio and precision.

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