The concentration of a sodium hydroxide solution can be determined by titration with hydrochloric acid of a known concentration.
25.0 cm3 of the sodium hydroxide solution was measured using a pipette and transferred to a conical flask.
A few drops of phenolphthalein indicator were added to the alkali in the conical flask. Hydrochloric acid was added to the flask from a burette until the indicator changed colour.
Describe the colour change seen in the conical flask at the end point of the titration.
276 exam-style questions on Edexcel GCSE Chemistry 4.1 Acids, covering 4.1.1 Acids, alkalis and the pH scale, 4.1.2 Hydrogen ion concentration and pH, 4.1.3 Dilute and concentrated, weak and strong acids, 4.1.4 Bases, alkalis and the reactions of acids, 4.1.5 Chemical tests for hydrogen and carbon dioxide, 4.1.6 Neutralisation as a reaction of acids with bases, 4.1.7 Preparing soluble salts, and 4.1.8 Solubility rules and preparing insoluble salts. Each one has a worked solution and a mark scheme showing where the marks go.