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Acids, alkalis and titrations

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Question 18

An industrial chemist performs a titration to verify the concentration of a freshly prepared batch of nitric acid.

This is the chemist's method:

  • Use a volumetric pipette to transfer 20.0 cm3 of the nitric acid into a conical flask.
  • Add a few drops of phenolphthalein indicator to the flask.
  • Add aqueous sodium hydroxide from a burette until the indicator just changes colour.
  • Determine the volume of alkali added from the burette.

The concentration of the sodium hydroxide solution is 0.0600 mol/dm3. The volume of sodium hydroxide required to neutralise the acid is 18.50 cm3.

The equation for the reaction between nitric acid and sodium hydroxide is:

HNO3+NaOH→NaNO3+H2O \text{HNO}_3 + \text{NaOH} \rightarrow \text{NaNO}_3 + \text{H}_2\text{O} HNO3​+NaOH→NaNO3​+H2​O
a.

Calculate the amount, in moles, of NaOH\text{NaOH}NaOH used in this titration.

[2]
b.

Calculate the concentration, in mol/dm3\text{mol/dm}^3mol/dm3, of the nitric acid.

[2]
c.

The chemist makes a solution of sodium nitrate by neutralising aqueous sodium hydroxide with dilute nitric acid. Describe how they could use crystallisation to obtain a pure, dry sample of sodium nitrate crystals from the solution of sodium nitrate.

[5]

Acids, alkalis and titrations Questions

  1. IGCSE
  2. /Chemistry
  3. /Acids, alkalis and titrations