Group 7 - The Halogens

Question 1

are halogens reactive

Answer 1

yes

Question 2

are halogens metals or nonmetals

Answer 2

reactive non metals

Question 3

how do halogens exist as

Answer 3

diatomic molecules

Question 4

are diatomic molecules polar or non polar

Answer 4

non polar

Question 5

what happens to electronegativity down group 7 and why

Answer 5

electronegativity decreases down group 7

because the number of principle energy levels increase

weaker attraction between the nucleus and electrons in the COVALENT BOND

Question 6

what happens to the boiling point down group 7 and why

Answer 6

boiling point down group 7 increases

*because size of atom increases

*there are more van der waals forces between molecules that need to be broken

Question 7

what colour and state is fluorine at room temperature

Answer 7

pale yellow gas

Question 8

what colour and state is chlorine at room temperature

Answer 8

pale green gas

Question 9

what colour and state is bromine at room temperature

Answer 9

dark red/orange liquid

Question 10

what colour and state is iodine at room temperature

Answer 10

dark purple/black solid

Question 11

how can we test the oxidising ability of halogens

Answer 11

by carrying out displacement reactions with aqueous solutions of halogens and aqueous solutions of halide salts

the most oxidising agent halogen will displace a halogen from its salt

Question 12

what colour is chlorine in aqueous solution

Answer 12

yellow

Question 13

what colour is bromine in aqueous solution

Answer 13

orange

Question 14

what colour is iodine in aqueous solution

Answer 14

purple black

Question 15

what will chlorine oxidise

what will bromine oxidise

what will iodine oxidise

Answer 15

chlorine will oxidise Br- and I-

bromine will oxidise I- but not Cl-

iodine will oxidise nothing

Question 16

what colour solution is formed when aqueous chlorine reacts with aqueous bromine ions

Answer 16

a yellow solution

Question 17

what colour solution is formed when aqueous chlorine reacts with aqueous iodine ions

Answer 17

a brown solution formed

Question 18

what colour solution is formed when aqueous bromine reacts with aqueous iodine ions

Answer 18

a brown solution is formed

Question 19

what happens when chlorine dissolves in water

Answer 19

when chlorine dissolves in water it forms a mixture of hydrochloric acid (HCL) and chloric(I) acid (HClO). the equilibrium mixture is called chorine water and is pale green in colour showing the presence of Cl2

Question 20

what type of reaction is chlorine reacting with water

Answer 20

a disproportionate reaction (type of redox reaction) because chlorine is oxidised and reduced

Question 21

what happens when we add universal indicator paper to chlorine water

Answer 21

if universal indicator paper is added to chlorine water it first turns red since both reaction products are acids (HCl=strong HClO = weak) and then the red colour disappears and the universal paper turns white since chloric(I) acid is a very effective bleach

Question 22

what happens to chlorine water in the presence of bright sunlight

Answer 22

if chlorine is bubbled through water in the presence of bright sunlight or if the green solution of chlorine water is left in bright sunlight then a colourless gas is produced (oxygen) and the green colour due to the chlorine fades. under these conditions, the chlorine oxidises water into oxygen and the chlorine itself gets reduced into chloride ions

Question 23

what has been used to sterilise drinking water and swimming baths

Answer 23

chlorine and its compounds

Question 24

is chlorine toxic and therefore how much should be used in swimming pools and drinking water

Answer 24

yes therefore the concentration of chlorine must only be small amounts

Question 25

which has the highest concentration of chlorine : swimming pools or drinking water

Answer 25

swimming poools and therefore it is monitored closely to ensure that there’s a high enough concentration to kill bacteria but not enough to be toxic

Question 26

has the use of chlorine in swimming pools decreased over the years

what has it been replaced by

Answer 26

yes

it’s been replaced with calcium chlorate(I)