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Acids, alkalis and titrations

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Question 27

A student does a titration to find the concentration of a solution of hydrochloric acid.

This is the student's method:

  • pipette 25.0 cm3 of the hydrochloric acid into a conical flask
  • add a few drops of indicator
  • add aqueous potassium hydroxide from a burette until the indicator just changes colour
  • determine the volume of alkali added from the burette

The concentration of the potassium hydroxide solution is 0.0400 mol/dm3. The volume of potassium hydroxide required to neutralise the acid is 22.40 cm3.

The equation for the reaction between hydrochloric acid and potassium hydroxide is:

HCl+KOH→KCl+H2O \text{HCl} + \text{KOH} \rightarrow \text{KCl} + \text{H}_2\text{O} HCl+KOH→KCl+H2​O
a.

(i) Calculate the amount, in moles, of KOH\text{KOH}KOH used in this titration.

[2]
b.

(ii) Calculate the concentration, in mol/dm3\text{mol/dm}^3mol/dm3, of the hydrochloric acid.

[2]
c.

The student makes a solution of potassium chloride by neutralising aqueous potassium hydroxide with dilute hydrochloric acid. Describe how he could use crystallisation to obtain a pure, dry sample of potassium chloride crystals from the solution of potassium chloride.

[4]

Acids, alkalis and titrations Questions

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