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The Dangers of Mixing Bleach and Ammonia

Often, one looks at a bottle of bleach and wonders, 'Why shouldn't this be mixed with ammonia?' If you know how dangerous chlorine gas is to humans (it was used as a chemical weapon during World War I and later by Nazi Germany in World War II), this will be very apparent. This entry will tell of a few reactions that can occur when bleach and ammonia are mixed in various proportions - the release of chlorine gas is just one of these.

In the following sections, the header will be the name of the most dangerous compound produced in the reaction shown. Please, do not try any of this at home.

Chlorine Gas (Cl2)

Bleach consists of a solution of about 5% sodium hypochlorite. This is prepared by dissolving chlorine gas in a basic solution of sodium hydroxide. The resulting solution is an equilibrium mixture:

Cl2(g) + 2 OH-(aq) ClO-(aq) + Cl-(aq) + H2O(l)

As long as the solution is kept basic, the equilibrium lies to the right. However, if bleach is mixed with acid, the OH- on the left is removed, and the equilibrium shifts to the left, and deadly chlorine gas is liberated. The important point here -- if bleach is mixed with acid (often found in toilet bowl cleaners), chlorine gas is liberated.

Do you see that Cl2 on the right hand side there? This means one part chlorine gas, made up of diatomic (two atom) molecules. It also means that the chlorine gas has been liberated from the bleach, and is quite capable of causing you harm when inhaled!

Nitrogen Trichloride (NCl3)

Another potential reaction, which occurs when a greater amount of bleach is added than ammonia, is this:

3NaOCl + NH3 --> 3NaOH + NCl3

That's sodium hydroxide and nitrogen trichloride. Nitrogen trichloride is a very toxic chemical to humans, and even if you did get close enough to ingest it, it would probably explode in your face first, as it is also a very volatile explosive. There is little necessity in explaining why that is bad.

Hydrazine (N2H4)

Still another reaction - in three parts this time - can occur, producing hydrazine (N2H4, a component of rocket fuel) if you have more ammonia than bleach:

NH3 + NaOCl --> NaOH + NH2Cl.

These two products then react with ammonia as follows: NH3 + NH2Cl + NaOH -->N2H4 + NaCl + H2O. One last reaction occurs to stabilise the reagents:

2NH2Cl + N2H4 --> 2 NH4Cl + N2.

This last equation is of particular interest because of the amount of heat it produces. The heat is so great that it usually leads to an explosion


As mentioned before, this article mentions some very dangerous chemicals. One should not ever, ever attempt to create the chemicals described above as it could result in injury or even death.  

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