A student requires hard water for an experiment in his laboratory…

MCQ

A student requires hard water for an experiment in his laboratory which is not available in the neighbouring area. In the laboratory, there are some salts, which when dissolved in distilled water can convert it into hard water. Select from the following groups of salts, a group, each salt of which when dissolved in distilled water will make it hard.

A
Sodium chloride, Potassium chloride.
B
Sodium sulphate, Potassium sulphate.
C
Sodium sulphate, Calcium sulphate.
✓
Calcium sulphate, Calcium chloride.

✓

Answer

Correct option: D.

Calcium sulphate, Calcium chloride.

Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula $\ce{CaSO4}$ and related hydrates. In the form of $\gamma-$ anhydrite $($the anhydrous form$),$ it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum
Calcium chloride is an inorganic compound, a salt with the chemical formula $\mathrm{CaCl}_2$. It is a colorless crystalline solid at room temperature, highly soluble in water. Calcium chloride is commonly encountered as a hydrated solid with generic formula $\mathrm{CaCl}_2\left(\mathrm{H}_2 \mathrm{O}\right) \mathrm{x}$, where $\mathrm{x}=0,1,2,4$, and $6$ . These compounds are mainly used for deicing and dust control. Because the anhydrous salt is hygroscopic, it is used as a desiccant Hard water can be prepared by dissolving sulphates, chlorides or bicarbonate salts of $\mathrm{Ca}^{2+}$ or $\mathrm{Mg}^{2+}$ ions.