Which gas is released when bleaching powder is added to water?

Question

Question

This question was previously asked in

RRB ALP CBT I 30 Aug 2018 Shift 3 Official Paper

Answer 1

The correct answer is Chlorine.

Key Points

Bleaching powder is used as an oxidising agent in many chemical industries, for disinfecting drinking water.
- It is called Calcium Hypochlorite and is represented as CaOCl_2.
Bleaching powder is produced by the action of Chlorine on dry slaked lime (Ca(OH)₂) and is soluble in water.
When bleaching powder reacts with water, it hydrolysis to hypochlorous acid (HCIO), which hydrolysis further into Hydrochloric acid (HCl), releasing a strong smell due to Chlorine (Cl).
In this reaction, we get the following chemical equation.
- Ca(OCl)₂+H₂O→Ca(OH)₂+Cl_{2 (gas).}
- So, when Bleaching powder reacts with water, Chlorine gas is released. Hence option 2 is correct.
Chlorine gas is used in the manufacturing of bleaching powder.
Bleaching powder is used for bleaching cotton and linen in the textile industry, and for bleaching wood pulp in paper factories.
Hypochlorous acid is a weak acid that forms when Chlorine dissolves in water.
The atomic number (Z) of Chlorine is 17 and it is a p-block element.

Additional Information

Hydrogen (the atomic number is 1), in elemental form, exists as a diatomic molecule (H₂) and is called Dihydrogen.
- There are three isotopes of Hydrogen: Protium, Deuterium and Tritium.
Carbon Monoxide (CO) is a colourless and odourless poisonous gas produced as a result of the incomplete combustion of carbon.
- Carbon monoxide binds to haemoglobin and forms carboxyhaemoglobin which is about 300 times more stable than the oxygen-haemoglobin complex.
- When this reaches about 3-4%, the oxygen-carrying capacity of blood is reduced.
Carbon dioxide (CO₂) is a colourless and non-flammable gas at normal temperature and pressure.
- It is released into the atmosphere by respiration, the burning of fossil fuels and by decomposition of limestone.