Question

Write the chemical name of bleaching powder and name the gas that is evolved when it is exposed to the air. Also, write down the chemical reaction which is involved in the preparation of bleaching powder.

Answer 1

Hint: Bleaching powder is a yellowish white coloured solid substance with the gas being evolved upon its reaction with air often used for the disinfection of swimming pools. With this in mind, try to answer this question.

Step-by-Step Solution:
Bleaching powder is a pale yellowish powder existing with a strong smell of chlorine. It is soluble in water but due to the presence of impurities, we never observe a clear solution. Its chemical formula is \[CaOC{{l}_{2}}\] with its chemical name as Calcium hypochlorite.
Bleaching powder is used for bleaching dirty clothes in the laundry, as a bleaching agent for cotton and linen in the textile industry. It is also used as a strong oxidizing agent hence used as an oxidizer in many industries. It is also used as a disinfectant which is used for disinfecting water to make potable water.
When exposed to air, bleaching powder gives a smell of chlorine. This is because bleaching powder reacts with carbon dioxide from the atmosphere to produce calcium carbonate and chlorine.
Bleaching powder is prepared on a large-scale basis by passing chlorine gas through a solution of calcium hydroxide (\[Ca{{(OH)}_{2}}\]) which is commonly known as slaked lime.
The reaction that occurs is:
\[\begin{array}{*{35}{l}}
   Ca{{(OH)}_{2}}+C{{l}_{2(g)}}\to CaOC{{l}_{2}}+{{H}_{2}}O \\
   ~ \\
\end{array}\]

Note: Bleaching powder is used as disinfectant and germicide especially in the sterilization of drinking water. It is also used for manufacturing of chloroform and is used as an oxidising agent in many chemical industries to obtain various chemical products.