Chlorine in sterilisation

Question 1

Give the equation for the reaction of chlorine and water.

Answer 1

Cl₂ + H₂O ⇌ HCl + HClO

Question 2

Give the equation for the reaction of chlorine and sodium hydroxide.

Answer 2

Cl₂ + 2NaOH ⇌ NaCl + NaClO + H₂O

Question 3

Give the equation for the reaction of chlorine and water in direct sunlight.

Answer 3

Cl₂ +2H₂O → 4HCl + O₂

Question 4

Explain why certain chlorine reactions are useful in sterilisation.

Answer 4

They produce ClO⁻ ions which are good oxidising agents and so kill microbes.

Question 5

Explain why the chlorine + sodium hydroxide reaction is beneficial.

Answer 5

It produces NaClO which is a solid and can be dissolved in water to sterilise it. Does not require large amounts of chlorine gas which is toxic.

Question 6

Explain why the chlorine + water reaction may not be viable in places such as Africa.

Answer 6

In direct sunlight it does not produce ClO⁻ ions, so does not sterilise.

Question 7

Give 2 advantages and 2 disadvantages to using chlorine to sterilise water.

Answer 7

+The benefits outweigh the risks
+It is used in low concentrations so is not as dangerous

-Some people are allergic to chlorine
-It is wasteful as most potable water is not used for drinking