Sodium tri poly phosphate (STPP) is manufactured by reaction of phosphoric acid with sodium

ANS:A - carbonate

Carbonate is a chemical compound containing the carbonate ion (𝐶𝑂32−CO32−​). It is a polyatomic ion composed of one carbon atom bonded to three oxygen atoms in a trigonal planar arrangement. The carbonate ion carries a negative two charge (2−2−) due to its two additional electrons. Carbonate compounds are abundant in nature and have various industrial, biological, and geological applications. Some common examples of carbonates include:

1. Calcium Carbonate (CaCO3): This is one of the most abundant minerals on Earth and is found in rocks such as limestone, marble, and chalk. Calcium carbonate is used in construction, as a filler in paper and paints, in agriculture as a soil conditioner, and in the manufacturing of cement and concrete.
2. Sodium Carbonate (Na2CO3): Also known as soda ash or washing soda, sodium carbonate is used in the manufacture of glass, detergents, soaps, and paper. It is also used in water treatment processes and as a food additive.
3. Potassium Carbonate (K2CO3): Potassium carbonate is used in the production of glass, soap, and as a mild drying agent in organic synthesis. It is also used in the manufacturing of some types of fertilizers and as a buffering agent in the food industry.

Carbonates are often involved in chemical reactions, including acid-base reactions. When carbonates react with acids, they form carbon dioxide gas (𝐶𝑂2CO2​), water, and the corresponding salt. For example, the reaction between calcium carbonate and hydrochloric acid can be represented as: 𝐶𝑎𝐶𝑂3+2𝐻𝐶𝑙→𝐶𝑎𝐶𝑙2+𝐻2𝑂+𝐶𝑂2CaCO3​+2HCl→CaCl2​+H2​O+CO2​ Overall, carbonates are important compounds with diverse applications in industry, agriculture, and everyday life.