household bleach 係acidic定alkal

The solution of household bleach is alkaline.

The active ingredient of household bleach is hypochlorite (OCl-) ion. Hypochlorous acid (HOCl) is a weak acid which is slightly ionized in water to form hypochlorite ion and hydrogen ion.
HOCl(aq) ≒ H+(aq) + OCl-(aq)

Since OCl-(aq) ion is formed from the slight ionization of a weak acid HOCl(aq), thus OCl-(aq) ion has a certain tendency to change back to HOCl. Therefore, OCl-(aq) ion in aqueous solution would reversibly react with water to give HOCl(aq) molecule and OH-(aq) ion.
OCl-(aq) + H2O(l) ≒ HOCl(aq) + OH-(aq)
The concentration of OH-(aq) in the solution is thus higher than that of H+(aq), and the solution is alkaline.
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As the previous answer already list out all information about household bleach which is alkaline but since it only contains about 5 to 10 %hypochlorite, this chemical is very unstable under acidic condition. The manufacturer have to add sodium hydroxide solution to keep the bleach solution stable that is longer shelf life. The hydroxide ions are mainly from NaOH!