Group 7

Question 1

What is the trend of electronegativity?

Answer 1

Decreases because the number of shells increases so there’s a weaker attraction between nucleus and electrons in a covalent bond.

Question 2

What is the trend in BP and MP?

Answer 2

Increases, more VDW between molecules that need to be broken.

Question 3

What does fluorine look like at room temperature?

Answer 3

Pale yellow gas.

Question 4

What does chlorine look like at room temperature?

Answer 4

Pale green gas.

Question 5

What does bromine look like at room temperature?

Answer 5

Red-orange liquid.

Question 6

What does iodine look like at room temperature?

Answer 6

Black solid.

Question 7

What is an oxidising agent?

Answer 7

An electron acceptor.

Question 8

What acts as oxidising agents?

Answer 8

Halogen atoms.

Question 9

What is the strongest oxidising agent?

Answer 9

Fluorine.

Question 10

What happens to the ability to act as an oxidising agent down the group?

Answer 10

Decreases, atomic radius and shielding increases so become harder to gain electron.

Question 11

What are the three displacement reactions?

Answer 11

1) Cl2 + 2Br- ~> Br2 + 2Cl- (yellow/orange solution)
2) Cl2 + 2I- ~> I2 + 2Cl- (brown solution)
3) Br2 + 2I- ~> I2 + 2Br- (brown solution).

Question 12

What is a reducing agent?

Answer 12

Electron donor.

Question 13

What happens to the ability to act as a reducing agent down the group?

Answer 13

Increases, size increases so electrons further away from nucleus so less attraction.

Question 14

What reaction do all halides do?

Answer 14

Acid-base reaction.

Question 15

What is the general equation for an acid-base reaction?

Answer 15

NaX + H2SO4 ~> NaHSO4 + HX

(swap the Na and a H)

Question 16

What is the observation in an acid-base reaction?

Answer 16

Misty fumes (HX).

Question 17

What are the possible products of a halide ion redox reaction?

Answer 17

HX, SO2, S, H2S.

Question 18

What redox reaction can each halide undergo?

Answer 18

F and Cl acid base only.
Br acid base and SO2.
I acid base, SO2, S and H2S.

Question 19

What are the observations in redox reactions?

Answer 19

SO2- choking gas
S- yellow solid
H2S- rotten egg smell
Br2- brown gas
I2- black solid + purple gas.

Question 20

How can halide ions be identified?

Answer 20

Add acidified silver nitrate.

Question 21

What is the ionic equation for halide ions and silver nitrate?

Answer 21

Ag+ + X- ~> AgX.

Question 22

What precipitates do silver halides create?

Answer 22

AgCl- white ppt
AgBr- cream ppt
AgI- yellow ppt.

Question 23

What do we acidify silver with? Why?

Answer 23

Nitric acid because hydroxide and carbonate ions also form a precipitate with silver ions so need to be removed.

Question 24

What do we add to silver halides to confirm their identity?

Answer 24

Ammonia.

Question 25

How do halides react in different concentrations of ammonia?

Answer 25

Dilute ammonia- AgCl soluble, AgBr sparingly soluble, AgI insoluble.
Conc ammonia- AgBr- soluble AgI- insoluble.

Question 26

What is the general equation when silver halides react with ammonia?

Answer 26

AgCl + 2NH3 ~> Ag(NH3)2+ + Cl-.

Question 27

What is the equation for chlorine water?

Answer 27

Cl2 + H2O ~><~ HCl(aq) + HClO(aq).

Question 28

What is the use of HClO?

Answer 28

Bleach.

Question 29

What does chlorine do in the presence of bright sunlight?

Answer 29

2Cl2 + H2O ~> 4HCl + O2

pale green gas ~> colourless.

Question 30

Why can chlorine be used in water treatment even though it’s toxic?

Answer 30

It’s used in low concentrations or small amounts.

Question 31

What is a use of chlorine in water treatment?

Answer 31

Kill bacteria.

Question 32

What is the equation for Cl reacting with cold dilute sodium hydroxide?

Answer 32

Cl2 + 2NaOH ~> H2O + NaCl + NaClO.

NaClO is used in household bleach.

Question 33

What are the steps in filtering?

Answer 33

1) Filter using gravity
2) Wash residue with water to remove soluble impurities
3) Dry in air to remove water.