Group 17 Elements

Question 1

What do halogens exist as at room temp

Answer 1

Diatomic molecules

Question 2

Atomic radius _ down the grp because…

Answer 2

Increases

Energy levels are added

Question 3

Mp and bp _ down the grp due to …

Answer 3

Increase
Van der waals forces increase between molecules as no of electrons increase hence a stronger attractive force harder to break

Question 4

Volatility _ down the group because…

Answer 4

Ease with which they evaporate decreases

There’s ah increase in vanderwaals between diatomic molecules

Question 5

Colour intensity _ going down the grp because…

Answer 5

Increases (get darker)

Question 6

Halogens react with metals by _ and form a _

Answer 6

Gaining an electron

Ionic salt

Question 7

Halogens are _ agents meaning

Answer 7

Oxidising

They get reduced by accepting an electron

Question 8

Halogens react with non metals by _

Answer 8

Sharing an electron

Question 9

What does electronegativity decrease down the grp

Answer 9

Fluorine has a small radius so outer shell receives a lot of nuclear charge since its near and there’s also less shielding so a new electron will be greatly attracted
So fluorine is a better OA than iodine

Question 10

Displacement:

Answer 10

More reactive ie more electronegative halogen displaces less reactive one from a slide solution

Question 11

Halogen + H2 gives?

Answer 11

Hydrogen halide gas

Question 12

Reactivity _ down the grp

Answer 12

Decreases

Question 13

How can hydrogen halide be decomposed

Answer 13

Insert a hot wire

Question 14

Thermal stability of hydrogen halides going down

Answer 14

Decreases (F is most stable, I is least)

Question 15

Hydrogen-halogen bond energy _ down the grp this is due to…

Answer 15

Decreases-easier to break
Overlap of halogen outer she’ll with hydrogen atom gives longer bonds down the group hence reducing the strength (this is why HI is least stable)

Question 16

Test for presence of halide ions:

Answer 16

Add dil nitric acid and silver nitrate solution

Ppt formed

Question 17

Results for AgNO3 test

Answer 17

Cl- white
Br-cream
I-yellow

Question 18

Tests to further distinguish between Cl,Br,I

Answer 18

Dil ammonia:
Cl- dissolves, Br and I- insol

Conc ammonia:
Cl and Br- dissolve, I- insol

Question 19

NaCl + H2SO4 ->

Answer 19

NAHSO4 (s) + HCl (g) fumes

Sulfuric acid doesn’t further oxidise hcl because

Question 20

NaBr + H2SO4 ->

Answer 20

NAHSO4 (s) + HBr (g)
Further on H2SO4 reduced to SO2 and HBr oxidised to Br2 gas plus H2O as byproduct
2HBr + H2SO4 -> Br2 + SO2 + 2H2O

Question 21

NaI + H2SO4 ->

Answer 21

H2SO4 reduced ro various products as it oxidises the HI produced
These include SO2, S, H2S
Iodine is produced as a purple vapour

Question 22

Ease of hydrogen halide _ down grp

Answer 22

Increases

Question 23

What is disproportionation

Answer 23

Cl2 when reacted with dil alkali sol
It is a self oxi/red reaction
Depends on temp

Question 24

Cl2 in cold alkali: 15°C products are nacl+naclo+h20

Answer 24

Cl is reduced and it’s oxidation becomes 0->-1 gains an electron
0.5Cl2 +e- -> Cl-
Also oxidised to form ClO- it’s oxidation state becomes +1 as
0.5Cl2+2OH- ->ClO-+H2O+e-

Question 25

Cl2 in hot alkali: 70°C products same as for cold but oxi/red nos diff…

Answer 25

3Cl2 + 6NaOH -> 5NaCl +NaClO3 +3H2O

so Cl2 oxi state 0 reduced to +5 and oxidsed to -1

Question 26

Uses of chlorine

Answer 26

• kills bacteria in water ie the HCl and HClO do so as Cl2 + H20 oxidation to them
• bleach a mixture of nacl and naclo. Oxygen atoms from chlorate ions oxidise dye
• organic compounds such as pvc and halogenated hydrocarbons used as solvents, refrigerants and aerosols