(a) Student dropp

(a) When a piece of marble (CaCO₃) is dropped in dil HCl, CO₂ gas will be evolved which turns lime waster milky.

Formation of CaCO₃ white ppt makes the lime water milky.

(b) (i) Being alkaline, sodium hydrogen carbonate (baking soda) neutralises the excess acid present in the stomach and relieves indigestion.

(ii) Baking powder is a mixture of baking soda and a mild edible acid such as tartaric acid. When baking powder mixes with water (present in dough made for baking cake or bread), then sodium hydrogen carbonate reacts with tartaric acid to evolve CO₂ gas.