Capitol Reflecting Pool:

Why do we use chlorine to clean water?

by Grace Nailing

“My Eyes!!” Why do we need goggles when going to the pool? If you don’t wear goggles, you probably notice that the chlorine causes your eyes to burn. Why does cause a burn on us humans? If the chlorine causes pain, then why is it in the pool. Continue reading and you will found out the breakdown of cleaning the pool and why chlorine burn to us humans.


Did you know that chlorine has two main chemical compounds that keeps the pool free from bacterium and also cleans the pool. These two chemicals are HOCl and OCl-. HOCl is Hypochlorous Acid and OCl- is Hypochlorite Ion, both of these chemical compounds kill microorganisms and bacteria. These chemicals are what cleans the pools, combined with ammonia and even broken down into single atoms. HOCl helps kill the cell in the chlorinated pool. For example, the cell wall opens up and the chlorine enters the cell wall and kill the cells.

There are 3 main steps to the chemical reaction where chlorine breaks down in the pool. First, Hypochlorous Acid breaks into 2 parts, hydrogen ion and hypochlorite ion. Ion is an particle that has a charge that gained or lost an electron. The hydrogen ion is positive because it lost an electron and the hypochlorite ion is negative it gained an electron. Next, there is an opposite reaction, it starts with hydrogen ion and hypochlorite ion combining to create hypochlorous acid. Lastly, these two reactions keep going back and forth until they reach equilibrium or balance each other out. From this I learned that reaction two is just the reverse of reaction 1, due to occurring at the same time.

Equilibrium matters all due to the pH level in the pool. According to research, if the pH level is between 7.2 and 7.8 equilibrium is happening, but if the pH level is below 7.2 the hypochlorous acid(HOCl) causes irritation to the eyes of summers. I also found out that if the pH is higher than 7.8 there will not be enough hypochlorous acid(HOCl) to kill the bacterium in the pools. Most people wonder why chlorine sometimes cause your hair to irritate or itch. Studies show that chlorine causes women/men hair to dry out, when this happens washing your hair is a must. According to research, hypochlorous acid is what causes the hair to dry out. If, for whatever reason, you want to avoid this effect you could, wear goggles while letting the chlorine kill the bacterium.

Vocabulary Definition:


Hypochlorous Acid- a weak acid that forms when chlorine dissolves in water (HOCl)


Ion- an atom where the charge is either positive or negative due to the loss or gain of an electron.


Atom- the basic building block of all matter


Hypochlorite Ion- an ion that forms when chlorine dissolves in water (OCl-)


Chemical Reaction- a process that involves rearrangement of the molecular or ionic structure of a substance.


Equilibrium- when opposing forces or influences are balanced


pH level- measures potential of hydrogen, in other words measures how acidic the solution is