Question

Which of the following salts does not contain water of crystallisation?

• A. Gypsum
• B. Blue vitriol
• C. Baking soda
• D. Washing soda

Answer 1

Answer: (C)

Blue vitriol is copper(II) sulphate pentahydrate $\left({CuSO}_4.5H_{2}O\right)$.
Baking soda is sodium bicarbonate without any water of crystallisation $\left(NaH{CO}_3\right)$.
Washing soda is sodium carbonate decahydrate $({Na}_2{CO}_3.10H_{2}O)$.
Gypsum is a mineral composed of calcium sulphate dihydrate $\left({CaSO}_4.2H_{2}O\right)$.