Which substance contains water of crystallisation?
Answer and explanation
Correct answer: Washing soda
Water of crystallisation is the definite number of water molecules chemically associated with one formula unit of a hydrated salt. Washing soda is hydrated sodium carbonate, Na₂CO₃·10H₂O, so it contains ten water molecules of crystallisation. Baking soda is NaHCO₃ and does not contain such water in its formula; sodium chloride and calcium oxide are also represented here as anhydrous substances. Therefore option A is correct.
Frequently asked questions
What is the correct answer to this question?
Washing soda
Why is this the correct answer?
Water of crystallisation is the definite number of water molecules chemically associated with one formula unit of a hydrated salt. Washing soda is hydrated sodium carbonate, Na₂CO₃·10H₂O, so it contains ten water molecules of crystallisation. Baking soda is NaHCO₃ and does not contain such water in its formula; sodium chloride and calcium oxide are also represented here as anhydrous substances. Therefore option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
