When chlorine gas is added to water, it undergoes a reversible disproportionation reaction to produce a mixture of hydrochloric acid () and chloric(I) acid ().
The chemical equation for this process is: where the oxidation state of chlorine changes from to in and in .
This reaction is the basis for water chlorination, as the resulting is the molecule responsible for killing bacteria and pathogens in drinking water and swimming pools.
Chlorine reacts with cold, dilute sodium hydroxide () at approximately degrees Celsius to form sodium chlorate(I), sodium chloride, and water.
The ionic equation for this reaction is: .
This reaction is commercially significant because sodium chlorate(I) () is the active ingredient in household bleach, used for both whitening fabrics and disinfecting surfaces.
In the presence of ultraviolet (UV) light, the reaction between chlorine and water follows a different pathway, leading to the decomposition of the chloric(I) acid.
The overall reaction in sunlight is: .
This explains why chlorine levels in outdoor swimming pools must be constantly monitored and replenished, as the sanitizing agent is rapidly lost through this photochemical process.
Oxidation State Tracking: Always assign oxidation numbers to chlorine in every product to verify if a reaction is a disproportionation; remember that oxygen is usually and hydrogen is .
State Symbols: Pay close attention to state symbols in equations, especially for vs and the formation of precipitates in related halide tests.
Equation Balancing: When writing the reaction with , ensure the ratio of hydroxide to chlorine is maintained to balance the charges and atoms correctly.
Common Mistake: Do not confuse chloric(I) acid () with chloric(V) acid (); the Roman numeral indicates the oxidation state of the chlorine atom.
