A mineral water bottle is labelled as 'potable water'. Chemical analysis shows that the water contains low concentrations of dissolved ions, such as calcium and hydrogencarbonate.
Why is this water classified as potable even though it is not chemically pure?
The dissolved ions are completely insoluble in water.
The boiling point of this water is exactly 100 ∘C100\ ^\circ\text{C}100 ∘C at standard pressure.
The dissolved ions are present in low, safe levels that are harmless to human health.
Sterilisation with chlorine has chemically removed all the dissolved ions.
107 exam-style questions on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one has a worked solution and a mark scheme showing where the marks go.