Question

(a) What is bleaching powder? How is bleaching powder prepared? Write a chemical equation of the reaction involved in the preparation of bleaching powder? (b) What happens when bleaching powder reacts with dilute sulphuric acid ? Give an equation of the reaction involved? (c) State two important uses of bleaching powder?

Answer 1

Calcium hypochlorite is an inorganic compound with formula ${\text{Ca(OCl}}{{\text{)}}_2}$ . It is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agent. This compound is relatively stable and has greater available chlorine than sodium hypochlorite. It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air.

Complete answer:
Calcium hypochlorite is produced industrially by treating lime ( $Ca{\left( {OH} \right)_2}$ ) with chlorine gas. The reaction can be conducted in stages to give various compositions, each with different concentrations of calcium hypochlorite, together with unconverted lime and calcium chloride. The full conversion is shown $2C{l_2} + {\text{ }}2{\text{ }}Ca{\left( {OH} \right)_2} \to {\text{ }}Ca{\left( {OCl} \right)_2} + CaC{l_2} + 2{H_2}O$ Bleaching powder is made with slightly moist slaked lime. It is not a simple mixture of calcium hypochlorite, calcium chloride, and calcium hydroxide. Instead, it is a mixture consisting principally of calcium hypochlorite $Ca{\left( {OCl} \right)_2}$ , dibasic calcium hypochlorite, $C{a_3}{\left( {OCl} \right)_2}{\left( {OH} \right)_4}$ (also written as $Ca{\left( {OCl} \right)_2}$ · $2{\text{ }}Ca{\left( {OH} \right)_2}$ ), and dibasic calcium chloride, $C{a_3}C{l_2}{\left( {OH} \right)_4}$ (calcium hydroxychloride also written as $Ca{\left( {OCl} \right)_2}$ · ) . Other names are Hypochlorous acid, calcium salt, bleaching powder, calcium oxychloride, and lime . Bleaching powder is ${\text{Ca(OCl}}{{\text{)}}_2}$ (calcium oxychloride). It gives a strong smell of chlorine. It reacts with sulphuric acid to form calcium sulphate and chlorine gas is liberated. Reaction is given below –
$CaOC{l_2} + H2S{O_2} \to CaS{O_4} + C{l_2} + H{_2}O$ Here, the chlorine produced by the action of dilute acid on bleaching powder acts as a bleaching agent. Thus, the real bleaching agent present in bleaching powder is chlorine.

Note :
Wear eye protection such as wrap-around safety glasses and/or goggles to avoid getting the bleach in your eyes.Wear rubber household gloves or nitrile gloves to avoid skin exposure.Wear clothing that will cover your skin in case of spills. At a minimum, wear a long-sleeved shirt, pants, socks and shoes. If you want additional protection, chemical protective aprons and disposable protective suits are available from pesticide safety or industrial safety equipment suppliers. Open the container and mix out of doors or in a very well-ventilated room to avoid a buildup of vapors, which can cause eye and/or respiratory irritation.Wash your hands vigorously with mild soap and water before you use the bathroom, eat, smoke or use smokeless tobacco.Shower and wash yourself thoroughly with soap and shampoo at the end of the day.