Solution:
Concept: Limestone is another name for calcium carbonate
. When the calcium intake is insufficient, it is also utilised as a nutritional supplement. A colourless, odourless gas is produced when calcium carbonate is heated in a test tube, along with a white precipitate.It is a key component of pearls and is also found in the shells of sea creatures like snails and even eggs. It is typically produced when calcium ions in hard water combine with carbonate ions to form lime scale, and it is also an active component in agricultural lime. Additionally, calcium carbonate is used medically. It is used as an antacid or a calcium supplement, although excessive ingestion can be dangerous and can impair digestion.
When calcium carbonate is heated, it decomposes into calcium oxide (quick lime) and carbon dioxide gas is evolved.
Hence, the correct answers are options 2 and 3.
