h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

One post in this comment section mentions the non-existent NaONH3 compound -- that is the least of the problems with the information on this page. There are many, many errors ... it is impossible to generate chlorine gas by the single action of mixing bleach and ammonia.

I am a chemistry instructor, and I found this web page from a Google search when a student asked me about the problems of mixing ammonia with bleach. On first inspection, I thought I had found a resource I could direct the student to, but after glancing at the content I knew I had to make a post here.

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.

But what about the question of mixing bleach with ammonia? Well, the chemistry is entirely different. Once again, it is the chlorine that reacts, not the sodium hypochlorite. Chlorine will react with the ammonia to produce chloramines -- NH2Cl, NHCl2 and NCl3. It is not the sodium hypochlorite that is reacting. The NH2Cl can react with another ammonia to produce hydrazine. You can see that simply adding ammonia to bleach will NOT liberate chlorine gas. In fact, the exact opposite happens; the chlorine gas present is actually consumed by the ammonia. The products of the reaction of bleach with ammonia are deadly in their own right, but chlorine gas is not involved.

The basic message of the web page is correct -- do not mix bleach with anything. However, the details are all wrong. Please stop spreading bad chemistry.

Definite.

i would like to know how would you be able to survive these effects when you do go to mix these chemicals. email me at ([email protected]) subect bleach.

"You can see that simply adding ammonia to bleach will NOT liberate chlorine gas"

Yes, that reaction will not liberate the gas. But doesn't trichloramine NCl3 readily decompose into Nitrogen and Chlorine??? It is an unstable compound.

2 mol NCl3----> 1 mol N2 + 3 mol Cl2

That would explain the age-old problem of clouds stinking of chlorine that fume over everyone who mixes ammonia and bleach (just do a search and read the stories). The only other explanation would be that the chloramines smelled exactly the same as the gas that is liberated by mixing HCl and bleach (this gas, without a doubt is chlorine). I have smelled both and can find no difference.

Hello "instructor" of chemisty. I am a PROFESSOR of chemistry and I ahve much backlash and befaulderry to unleash upon your wrong nature of status quo!! YOu see in my many years of PROFESSING I have came upon this reaction many a time, you are indeed correct in saying acid will produce chlorine gas but what you failed to mention are the secondary steps of the reaction which reasult in production of bicarbonate of raspberry koolaid! An even more toxic substance when inhaled by mere mortals!!