Identify the correct match:

1. Washing soda – Na₂CO₃

2. Baking soda – NaHCO₃

3. Gypsum – CaSO₄·2H₂O

4. Plaster of Paris – CaSO₄·½H₂O

How many matches are correct?

Why they are all correct: Here is a quick breakdown of the chemical names for these compounds: Washing soda (Sodium Carbonate): $Na_2CO_3$ is used in glass manufacturing and as a water softener. Baking soda (Sodium Bicarbonate): $NaHCO_3$ is used in baking and as an antacid. Gypsum (Calcium Sulphate Dihydrate): $CaSO_4 \  cdot 2H_2O$ is the naturally occurring mineral used in cement and wallboard. Plaster of Paris (Calcium Sulphate Hemihydrate): $CaSO_4 \cdot \frac{1}{2}H_2O$ is formed by heating Gypsum. When you add water to it, it turns back into hard Gypsum.