CHEMICAL IMPACT
Household Chemistry
ommon household bleach is an aqueous solution containing approximately 5% sodium hypochlorite, a potent
oxidizing agent that can react with and decolorize chemicals that cause stains. Bleaching solutions are manufactured
by dissolving chlorine gas in a sodium hydroxide solution
to give the reaction
C
Cl2 1g2 2OH 1aq2 ∆ OCl 1aq2 Cl 1aq2 H2O1l2
As long as the pH of this solution is maintained above 8,
the OCl ion is the predominant chlorine-containing species.
However, if the solution is made acidic (the [OH] lowered),
elemental chlorine (Cl2) is favored, and since Cl2 is much
less soluble in water than is sodium hypochlorite, Cl2 gas is
suddenly evolved from the solution. This is why labels on
bottles of bleach carry warnings about mixing the bleach
with other cleaning solutions. For example, toilet bowl
cleaners usually contain acids such as H3PO4 or HSO4 and
have pH values around 2. Mixing toilet bowl cleaner with
bleach can lead to a very dangerous evolution of chlorine
gas.
In addition, if bleach is mixed with a cleaning agent
containing ammonia, the chlorine and ammonia can react
to produce chloramines, such as NH2Cl, NHCl2, and NCl3.
These compounds produce acrid fumes that can cause respiratory distress.
The label on this bleach bottle warns of the hazards of mixing
cleaning solutions.