disproportionation and water treatment Flashcards
(9 cards)
how can we make bleach? qrite the equation for the reaction of bleach
mix chlorine gas with cold , dilute aqueous sodium hydroxide, the above reaction takes place and we get sodium chlorate (I) solution NaClO (aq), which is what is known as common household bleach.
2NaOH aq + Cl2 —> NaClO aq+ NaCl aq + H2O l
how does NaClO work in water treatment?
when added to water NaClO reacts to form HOCl, which is a powerful oxidiser which kills bacteria.
NaClO + H2O –> Na+ + OH- + HOCl
other than using NaClO and water, how else can we make HClO? write this in an equation format.
Cl2 g + H2O l –> HCl aq + HClO aq
what is the name of HClO?
aqueous chloric (I) acid
reaction of aqueous chloric (I) acid with water.
HClO aq + H2O l ⇌ ClO- aq + H3O+ aq these are chlorate (I) ions and hydronium ions
what do chlorate (I) ions do?
kill bacteria
what are the benefits using chlorine in water treatment
+prevents growth of algae
+eliminates bad tastes and smells
+removes discolouration caused by organic compounds
+ some chlorine can remain in the water and prevent reinfection further down the supply
+kills bacteria
what are the disadvantages of using chlorine in water treatment?
-chlorine can react with organic compounds in water to form chlorinated hydrocarbons, some are carcinogenic
-chlorine leaks are fatal, because chlorine in excess can have damaging effects on people, eg chemical burns or damaging the respiratory system
-ethical considerations, we don’t get a choice if our water is chlorinated or not, some people may view this as forced mass medication
what are alternatives to chlorinated water? discuss them.
ozone- a strong oxidising agent which is good at killing microorganisms, but it’s expensive and has a short half life so it won’t prevent reinfection further down the supply of water
UV light- damages DNA of microorganisms but is ineffective in cloudy water and won’t prevent reinfected further down the line
