The Halogens - chlorine

Question 1

Equation of Cl2 with H2O

Answer 1

Cl2 + H2O ⇌ HCl + HClO

Question 2

Name HCl

Answer 2

Hydrochloric acid

Question 3

Name HClO

Answer 3

Chloric (I) acid

Question 4

What type of reaction is the reaction between Cl2 and H2O?

Answer 4

Disproportionation

Where Cl2 species both oxidised and reduced

Question 5

What is the established equilibrium between Cl2 and H2O called, what colour is it and what species is responsible for this colour?

Answer 5

Chlorine water
Slight green tinge
Cl2

Question 6

When litmus paper is dipped into the Cl2 and H2O solution, what can be observed?

Answer 6

Part goes red due to HCl acid

Part white due to HClO (bleach)

Question 7

Why are chlorine and chlorine compounds used in water treatments? Give two examples.

Answer 7

Destroys bacteria.

Swimming pools
Drinking water from tap

Question 8

Despite Cl2 being toxic, why is it still used in water treatments?

Answer 8

Only used in small concentrations

Benefits outweigh risks

Question 9

What happens when NaOH is added to the equilibrium?

Answer 9

NaOH neutralises the acid (HCl).
Therefore the concentration of HCl decreases.
The equilibrium shifts to increase the conc of HCl hence favouring the forwards reaction.
The yield of Cl2 decreases, yield of HClO and HCl increases
Green colour decreases, goes more colourless.

Question 10

What happens when dilute HCl is added to the equilibrium?

Answer 10

Concentration of HCl increases
So equilibrium shifts to decrease the concentration so favours the backwards reaction
The yield of Cl2 increases and hence green colour increases.

Question 11

Reaction between NaOH, HCl and HClO

Answer 11

NaOH + HCl + HClO ➡️ NaCl + NaClO + H2O

Question 12

Give the normal and ionic equations used the the commercial manufacture of bleach.

Answer 12

Cl2 + NaOH ➡️ NaCl + NaClO + H2O

Cl- + OH- ➡️ Cl- + ClO- + H2O

Question 13

Give the name of NaClO

Answer 13

Sodium chlorate (I)