What is Calcium Hypochlorite?
Calcium hypochlorite is a chemical compound that has the formula Ca(ClO)2. It is commonly referred to as bleaching powder or calcium oxychloride. It is an ionic compound that is made up of a calcium cation (Ca2+) and two hypochlorite anions (ClO–). Despite being quite stable at room temperatures, calcium hypochlorite slowly decomposes in moist environments, giving it a characteristic ‘chlorine’ smell.
It is commercially available in its anhydrous and hydrated forms and is one of the key ingredients of chlorine powder and bleaching powder. Ca(ClO)2 is produced on an industrial scale via the reaction of chlorine gas with calcium hydroxide. The chemical equation for this reaction is provided below.
2Ca(OH)2 + 2Cl2 → Ca(ClO)2 + H2O + CaCl2
Generally, bleaching powder is a mixture of calcium hypochlorite, its dibasic form (Ca(ClO2).2Ca(OH)2), and the dibasic form of calcium chloride (CaCl2.2Ca(OH)2). Since it contains two ClO– ions, this compound has a high chlorine availability when compared to sodium hypochlorite (NaOCl).
The structure of a Ca(ClO)2 molecule is illustrated below. It consists of one Ca+ ion and two ClO– ions.
Each chlorite ion has a charge of -1 whereas the calcium ion has a charge of +2. Therefore, one calcium cation can form ionic bonds with two hypochlorite ions.
|Molar Mass/ Molecular Weight||142.98 grams per mole|
|Density at 20oC||2.35 grams per cubic centimetre|
|Melting Point||373K (100oC)|
|Boiling Point||Decomposes at 448K (175oC)|
- Calcium hypochlorite is a white/grey solid at room temperatures.
- Its solubility in water is 21g/100 mL and it reacts with the water when dissolved.
- Its solubility in hard water is relatively low when compared to its solubility in soft/medium-hard water.
- Ca(ClO)2 has a strong smell of chlorine (because it reacts with the water molecules present in air).
- It acts as a strong base since it readily accepts H+ When dissolved in water, the hypochlorite anion accepts a proton from H2O, liberating an OH– ion.
- The chemical reaction is given by ClO– + H2O → HClO + OH–
- This compound is also a powerful oxidizing agent since it can readily accept an electron.
- Calcium hypochlorite reacts with hydrochloric acid, yielding calcium chloride (CaCl2), water, and chlorine gas (Cl2).
- The chemical equation for this reaction is 4HCl + Ca(ClO)2 → CaCl2 + Cl2 + H2O
What are the Uses of Calcium Hypochlorite?
The compound Ca(ClO)2 is often used to disinfect large volumes of water in order to make it safe to drink. It is also widely used in swimming pools to sanitize the water body and destroy the germs present in it. Some other uses of calcium hypochlorite are listed below.
- Since it is a good oxidizing agent, this compound is quite useful in the field of organic chemistry.
- It is used to obtain fragmented aldehydes/carboxylic acids by cleaving the bonds in glycols and keto acids.
- Ca(ClO)2 can also be used in the haloform reaction to yield chloroform.
- The compound can be used to disinfect both wastewater and drinking water since it has a high chlorine availability.
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