1.1. A student wants to prepare sodium chloride crystals from sodium hydroxide solution and dilute hydrochloric acid.

He does a titration to find the volume of dilute hydrochloric acid needed to neutralise the sodium hydroxide solution.

This is his method.

• Add 25.0 cm³ of sodium hydroxide solution to a conical flask

• Add a few drops of phenolphthalein indicator to the conical flask

• Titrate the solution with the hydrochloric acid

Name a suitable piece of apparatus that the student should use to measure 25.0 cm³ of sodium hydroxide solution.

1.2. i) Give the colour of the phenolphthalein indicator in sodium hydroxide solution and in hydrochloric acid.

 (2)

 Colour in sodium hydroxide solution: .................................................

 Colour in hydrochloric acid: ....................................................................

 ii) Suggest why universal indicator is never used in a titration. 

(1)

1.3. The student finds that 21.50 cm³ of hydrochloric acid is needed to neutralise 25.0 cm³ of sodium hydroxide solution.

 i) Describe what the student should do next to prepare a pure solution of sodium chloride. 

(2)

 ii) Describe how the student could obtain dry crystals of sodium chloride from the pure sodium chloride solution.

(4)

1.4. The student needs 21.50 cm³ of hydrochloric acid to neutralise 25.0 cm³ of sodium hydroxide solution of concentration 0.800 mol / dm³. 

The equation for the reaction is 

NaOH + HCl → NaCl + H₂O 

Calculate the concentration, in mol / dm³, of the hydrochloric acid.

 concentration = .............................................................. mol / dm³