What happens when: i) Gypsum salt is heated at 120^ C ii) Chlorine gas is passed through… – Chemistry NEB 2074 (old course) (grade increment) Solution

i) When gypsum ( $CaSO X_{4} \cdot 2 H X_{2} O$ ) is heated at $12 0^{\circ} C$ , it loses its water of crystallization and forms plaster of Paris ( $CaSO X_{4} \cdot \frac{1}{2} H X_{2} O$ ). This process is known as calcination. The chemical equation is:

$CaSO X_{4} \cdot 2 H X_{2} O 120° C CaSO X_{4} \cdot \frac{1}{2} H X_{2} O + \frac{3}{2} H X_{2} O$

The product, plaster of Paris, is a white powder that sets into a hard mass when mixed with water, making it useful in construction and medical applications.

ii) When chlorine gas ( $Cl X_{2}$ ) is passed through slaked lime ( $Ca (OH) X_{2}$ ), it undergoes a displacement reaction to form bleaching powder ( $CaOCl X_{2}$ ). The chemical equation is:

$2 Ca (OH) X_{2} + 2 Cl X_{2} Ca (OCl) X_{2} + CaCl X_{2} + 2 H X_{2} O$

Bleaching powder is a yellowish-white powder used as a bleaching agent, disinfectant, and oxidizing agent. It releases chlorine gas when exposed to moisture or acids, which is responsible for its bleaching action.

What happens when: i) Gypsum salt is heated at 120^ C ii) Chlorine gas is passed through slaked lime.

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