Name the metal whose carbonate is known as washing soda.

12

Name a metal carbonate which is soluble in water.

13

Name an acid which is present in baking powder.

15

Which compound is used as an antacid in medicine: NaHCO₃ or Na₂CO₃?

16

What is the common name of

(a) NaHCO₃ or Na₂CO₃.10H₂O?