NCERT Long Question Answers

A precipitation reaction occurs when two dissolved substances combine, yielding an insoluble product called a precipitate. Typically, it involves a double displacement reaction where ions switch, forming new compounds. Examples include sodium sulphate with barium chloride, yielding barium sulphate precipitate, and silver nitrate with sodium chloride, forming silver chloride precipitate, crucial in chemical and analytical applications.

Exothermic reactions release heat, like methane combustion, respiration, carbon burning in oxygen, and organic decomposition. Endothermic reactions absorb heat, such as calcium carbonate decomposition, ferrous sulfate thermal decomposition, silver chloride decomposition, photosynthesis, and electrolysis of water. They require energy input, distinguishing them from exothermic reactions, which release energy.