The main ingredients of bleaching powder and the bleaching principle
Bleaching powder preparation method: chlorine gas into the solution of calcium hydroxide, calcium chloride and calcium hypochlorite.
The reaction equation is: 2Ca(OH)2 + 2Cl2 =CaCl2 + Ca(ClO)2 + 2H2O
Note: This reaction is a self - REDOX reaction, which can be understood as follows.
Chlorine gas was generated hydrochloric acid after reaction with water and hypochlorous acid, such as NaOH solution, if the chlorine gas can generate sodium chloride and sodium hypochlorite, reaction process can be understood as chlorine gas and water first generate hydrochloric acid and hypochlorous acid, hydrochloric acid and hypochlorous acid and sodium hydroxide reaction respectively generate sodium chloride and sodium hypochlorite, reaction with alkali solution can be expressed in the ionic equation: Cl2 + 2 oh - = Cl - + ClO - + H2O.
Chlorine reacts with calcium hydroxide to produce bleach in the same way.
Some students here ask, hypochlorous acid has bleaching, why not use hypochlorous acid as a bleaching agent?
The reason: Hypochlorite is more stable than hypochlorite and is easier to preserve.
Is calcium chloride or calcium hypochlorite used in bleaching powder?
First, let's look at it
(1) Main ingredients of bleach: a mixture of CaCl2 and Ca(ClO)2
(2) Active ingredient of bleach: Ca(ClO)2
(3) Bleaching principle of bleaching powder:
Ca(ClO)2 +2HCl= CaCl2 + 2HClO.
Of course, there is a problem, don't forget that there will be REDOX reaction, the formation of calcium chloride, water and chlorine gas, hypochlorous acid is not available, that is, 84 disinfectant and toilet cleaner can not be mixed use ah!
The true chemical equation of how bleach works: Ca(ClO)2+ CO2 +H2O= CaCO3↓+2HClO
Second, let's look at bleach in particular.
(1) Are sodium hypochlorite, calcium hypochlorite and chlorine gas bleach?
(2) What is the real bleaching agent?
(3) Sodium hypochlorite, calcium hypochlorite to play a bleaching role, how to deal with?
The answers to these questions are:
(1) The solids of sodium hypochlorite, calcium hypochlorite and chlorine gas are not bleached;
(2) The real bleaching agent is hypochlorous acid.
(3) Sodium hypochlorite and calcium hypochlorite must be converted to hypochlorite in order to act as bleaching agents.
The method of converting to hypochlorous acid can be directly dissolved in water and prepared into an aqueous solution, which can react with water and CO2 to form hypochlorous acid.
Or strengthen the acid dilute hydrochloric acid and convert it to hypochlorous acid.
Finally, what's the difference between bleach, bleach and bleaching powder?
Bleach is an aqueous solution of sodium hypochlorite (84 disinfectant is commonly used in daily life). Bleaching powder is a mixture of calcium chloride and calcium hypochlorite. Bleaching powder is the same as bleaching powder, and calcium hypochlorite content is higher.
The true chemical equation of how bleach works: Ca(ClO)2+ CO2 +H2O= CaCO3 +2HClO