Chlorine meets lime
Chlorine passed over dry slaked lime makes bleaching powder.
Put the chlorine to work
The chlor-alkali process gives a lot of chlorine gas. A factory wants a solid that can bleach and kill germs and is easy to carry.
What can it do with the chlorine?
What this lesson covers
The idea
Bleaching powder, represented as Ca(ClO)2, is produced by the action of chlorine on dry slaked lime [Ca(OH)2].
Put the chlorine to work
The chlor-alkali process gives a lot of chlorine gas. A factory wants a solid that can bleach and kill germs and is easy to carry.
What can it do with the chlorine?
- Pass it over dry slaked lime, Ca(OH)₂
- Bubble it through sodium chloride solution
- Mix it with baking soda
Make bleaching powder
Pass the chlorine, then let it react. Then balance the equation.
Chlorine + dry slaked lime
Bleaching powder, written Ca(ClO)₂, is produced by the action of chlorine on dry slaked lime, Ca(OH)₂.
The actual composition of bleaching powder is quite complex, but it is written as Ca(ClO)₂. It is also an oxidising agent in many chemical industries.
- Bleaching powder is used
- in textile industry | to bleach cotton and linen
- in paper factories | to bleach wood pulp
- in laundry | to bleach washed clothes
- for drinking water | to make it free from germs
Notes
Bleaching powder, represented as Ca(ClO)₂, is produced by the action of chlorine on dry slaked lime [Ca(OH)₂].
Check yourself
Bleaching powder is made by passing … over dry slaked lime.
What is the formula of slaked lime?
Bleaching powder is used to …
Which pair of reactants makes bleaching powder?
- chlorine — correct. Yes!
- hydrogen. Hydrogen is the other gas from the chlor-alkali process. It is chlorine that is used.
- sodium hydroxide. NaOH is a solid or solution, not the gas passed over the lime.
- CaO. CaO is quicklime. Add water and it becomes slaked lime, Ca(OH)₂.
- Ca(OH)₂ — correct. Yes!
- CaCO₃. That is limestone.
- make bread rise. That is baking powder or baking soda.
- neutralise a bee sting. A mild base like baking soda is used for that.
- make drinking water free from germs — correct. Yes! It also bleaches cotton, linen and wood pulp.
- Chlorine and dry slaked lime — correct. Yes!
- Hydrogen and dry slaked lime. The gas is chlorine, not hydrogen.
- Chlorine and sodium chloride solution. Dry slaked lime is the other reactant.