10.4- USES OF CHLORINE

Question 1

What is chlorine?

Answer 1

poisonous gas

Question 2

Is chlorine soluble in water?

Answer 2

yes

Question 3

Why is chlorine dissolved in water an essential part of our life? (hint- e.g. use)

Answer 3

in treatment of water for drinking and swimming pools

Question 4

What type of reaction is it when chlorine reacts with water?

Answer 4

reversible reaction

Question 5

What is formed when chlorine and water react together? (2)

Answer 5

chloric (I) acid, HClO

hydrochloric acid HCl

Question 6

What is the equation for when chlorine and water react?

Answer 6

Cl2 (g) + H2O(l) = reversible HClO (aq) + HCl (aq)

Question 7

What is disproportionation?

Answer 7

type of redox reaction, where the oxidation state of some atoms of same element increase and others decrease

Question 8

What is the reaction between chlorine and water an example of?

Answer 8

disproportionation

Question 9

Why is the reaction between chlorine and water an example of disproportionation?

Answer 9

number of one of the chlorine atoms increases from 0 to +1 and that of other decreases from 0 to -1

Question 10

Example of when the reaction between chlorine and water take place?

Answer 10

when chlorine is used to purify water for drinking + swimming baths

Question 11

Why is chlorine added to water to purify it?

Answer 11

prevent life-threatening diseases

Question 12

What type of agent is chloric (I) acid?

Answer 12

oxidising agent

Question 13

What does chloric (I) acid do?

Answer 13

kills bacteria by oxidation

Question 14

What is chloric (I) acid also used as?

Answer 14

bleach

Question 15

How do the other halogens react with water?

Answer 15

react similarly, but much more slowly going down the group

Question 16

Does the same reaction between chlorine and water occur in sunlight?

Answer 16

no

Question 17

What is the equation for the reaction between chlorine and water in sunlight?

Answer 17

2Cl2 (g) + 2H20 (l) = 4HCl (aq) + O2 (g)

Question 18

What is the colour of chlorine?

Answer 18

pale green

Question 19

What is the colour of HCl?

Answer 19

colourless

Question 20

Why do shallow pools need frequent addition of chlorine in sunlight?

Answer 20

chlorine rapidly lost from pool water in sunlight

Question 21

What is an alternative to the direct chlorination of swimming pools?

Answer 21

add solid sodium (or calcium) chlorate ().

Question 22

What does the solid sodium (or calcium) chlorate do in the swimming pool?

Answer 22

dissolves in water

Question 23

When the sodium (or calcium) chlorate dissolves in the water, what does it form?

Answer 23

chloric (I) acid, HClO (aq)

Question 24

What is the reaction of sodium (or calcium) chlorate and water an example of? (hint- type of reaction)

Answer 24

reversible reaction

Question 25

What is the equation for the reaction between sodium (or calcium) chlorate and water?

Answer 25

NaClO (s) + H2O =*reversible* Na+ (aq) + OH- (aq) + HClO (aq)

Question 26

In alkaline solutions where does the position of equilibrium move for the reaction between sodium (or calcium) chlorate?

Answer 26

moves to left and HClO is removed as ClO- ions

Question 27

What is done to prevent the position of equilibrium moving to the left in the reaction between sodium (or calcium) chlorate?

Answer 27

swimming pools need to kept slightly acidic

Question 28

Why is the pH of swimming pools carefully monitored?

Answer 28

so water doesn't get acidic enough to corrode metal components and affect swimmers

Question 29

What is formed when chlorine and cold, dilute sodium hydroxide react?

Answer 29

form sodium chlorate (I), NaClO

Question 30

What sort of agents is NaClO?

Answer 30

oxidisng agent

Question 31

What is NaClO in?

Answer 31

active ingredient in household bleach

Question 32

What is the reaction between chlorine and cold, dilute sodium hydroxide an example of?

Answer 32

disproportionation reaction

Question 33

How do the other halogens behave when reacting with an alkali?

Answer 33

behave similarly