halogens

Question 1

halogen group no.

Answer 1

17

Question 2

name the halogens

Answer 2

fluorine, chlorine, bromine, iodine, astatine

Question 3

molecule type - g17

Answer 3

diatomic

Question 4

diatomic molecules

Answer 4

when two atoms are joined together by a single covalent bond

Question 5

bp/mp- g17

Answer 5

increase down the group, because of the increasing strength of the London forces (induced dipole - dipole ) as the size and the relative mass of the atoms increase

Question 6

volatility …. down the group

Answer 6

decreases

Question 7

reactivity

Answer 7

halogens react by gaining an electron in their outer shell to form 1- ions and obtain a noble gas configuration
they are good at attracting and capturing electrons - they get reduced but oxidise other substances

Question 8

…… oxidising agents

Answer 8

strong

Question 9

as you go down the group - radii

Answer 9

the atomic radii increases so the outer electrons are further from the nucleus. the outer electrons are shielded more from the attraction of the positive nucleus, because there are more inner electrons. this makes it harder for larger atoms to attract the electron needed to form an ion, so larger atoms are less reactive.

Question 10

decrease in reactivity

Answer 10

can be shown in the reactions that halogens undergo with other halide ions

Question 11

the reactivity and oxidising power of the halogens decrease moving down the group and this is because…..

Answer 11

• the atomic radius increases (nuclear pull is further away from the incoming electrons )
• the electron shielding increases
• the ability to gain an electron in the p subshell and form 1- ions decreases

Question 12

redox reactions

Answer 12

occur between the aqueous solutions of halide ions and aq soloutions of halogens

Question 13

a more reactive halogen will

Answer 13

oxidise and displace a halide of a less reactive halogen, displacement

Question 14

colour changes - halogens form diff coloured soloutions

Answer 14

indicate redox has occurred
- mixture is usually shaken with an organic solvent eg. cyclohexane to help distinguish between bromine and iodine

Question 15

cl2 - colour in water

Answer 15

pale green

Question 16

cl2- colour in cyclohexane

Answer 16

pale green

Question 17

br2- colour in water

Answer 17

orange

Question 18

br2- colour in cyclohexane

Answer 18

orange

Question 19

I2- colour in water

Answer 19

brown

Question 20

I2- colour in cyclohexane

Answer 20

violet

Question 21

disproportionation

Answer 21

a reaction in which the same element is both reduced and oxidised

Question 22

chlorine- oxidation

Answer 22

Chlorine oxidises both Br - and I - ions:
o Cl 2 (aq) + 2Br - (aq) –> 2Cl - + Br 2 (aq)
o Cl 2 (aq) + I - (aq) –> 2Cl - + I 2 (aq)

Question 23

bromine - oxidation

Answer 23

Bromine can only oxidise I - ions:
o Br 2 (aq) + 2I - (aq) –> 2Br - + I 2 (aq)

Question 24

disprortionation- alkalis

Answer 24

halogens will react with cold dilute alkali solutions and in these reactions, the halogen is simultaneously oxidised and reduced
- chlorine is only slightly soluble in water and has a mild bleaching action

Question 25

disproportionation- water

Answer 25

when you mix chlorine and water it undergoes - disproportionation
- chlorine reacts with water forming a mixture of hcl and chloric (I) ions (an oxidising agent ) which kills bacteria
- both reduced and oxidised

Question 26

house hold bleach is formed when

Answer 26

dilute aqueous sodium hydroxide and chlorine react together at room temperature