Why you must never mix bleach and ammonia
Formation of monochloramine · Substitution · Toxic product
Two ordinary cleaning products, mixed in a small bathroom, can make a gas that sends people to hospital.
Reactants approach
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ΔH not tabulated for this process.
Meet the molecules
- Reactantdissolved in water
OCl−
hypochlorite ion
- Reactantdissolved in water
NH3
ammonia
- Productdissolved in water
NH2Cl
monochloramine
- Productdissolved in water
OH−
hydroxide ion
What you notice
Household bleach is a 3–8% solution of sodium hypochlorite, NaOCl, and many glass and floor cleaners contain ammonia. When the two meet, for example when both are used on the same toilet or floor, they form chloramines, gases with a sharp, chlorine-like smell that irritate the eyes, nose and lungs. Breathing them causes coughing, chest pain and shortness of breath, and in a small closed bathroom it can be bad enough to need hospital care. Sweat and urine in swimming pools react with chlorine the same way, which produces the familiar pool smell.
Try it
Read the labels of the cleaning products at home, find which contain sodium hypochlorite and which contain ammonia, and make sure they are stored apart.
Safety: If bleach and ammonia are mixed by accident, leave the room, get to fresh air, and call poison control (1-800-222-1222 in the US).
Step by step
- 1
Two cleaners meet
Bleach supplies hypochlorite ions, OCl–, and ammonia cleaners supply NH3 molecules dissolved in water.
- 2
Chlorine changes partners
The lone pair on the nitrogen of NH3 attacks the chlorine of hypochlorite (mostly its protonated form, HOCl), and an N–Cl bond forms.
- 3
Hydroxide is left behind
The oxygen leaves with a hydrogen taken from the ammonia, ending up as hydroxide (or as water, when HOCl is the reactant).
- 4
More bleach, worse gases
With more bleach, NH2Cl reacts further to dichloramine, NHCl2, and nitrogen trichloride, NCl3, which is even more irritating and can explode when concentrated.