Question

Consider the following substances:

NaCl, Ca(OH)₂, NaHCO₃, NH₃, Na₂CO₃, H₂O, Cl₂, CO₂, CaSO₄.2H₂O, 2CaSO₄.H2O, CaOCl₂

1. Which two substances combine to form bleaching powder?
2. Which four substances are utilised in the production of washing soda?
3. Which compound represents plaster of Paris?
4. Which compound is a part of baking powder?
5. Which compound is used as an antacid?

Answer 1

1. Bleaching powder (CaOCl₂) is prepared by reacting dry slaked lime with chlorine gas.
   \[\ce{Ca(OH)2 + Cl2 -> CaOCl2 + H2O}\]
   Thus, Ca(OH)₂ and Cl₂ combine together.
2. Washing soda (Na₂CO₃) is manufactured via the Solvay process. This industrial method requires four basic raw materials.
   \[\ce{NaCl + NH3 + H2O + CO2 -> NH4Cl + NaHCO3}\]
   The target compounds are NaCl, NH₃, H₂O and CO₂.
3. Plaster of Paris is calcium sulfate hemihydrate. It is written as \[\ce{CaSO4 * 1/2 H2O}\]. Doubling the formula gives 2CaSO₄.H₂O.
4. Baking powder contains baking soda mixed with a mild edible acid. The component present from this list is sodium hydrogencarbonate (NaHCO₃).
5. Sodium hydrogencarbonate (NaHCO₃) is a mild alkaline salt. It safely neutralises excess stomach acid. Therefore, NaHCO₃ serves as an effective antacid.