Group 7

Question 1

Physical state of Fluorine and Chlorine

Answer 1

Gases at RTP.

Question 2

Physical state of Bromine

Answer 2

Liquid at RTP.

Question 3

Physical state of iodine

Answer 3

Solid at RTP.

Question 4

The mpt and bpt increases down the group, because:

Answer 4

1. Number of electrons increase, so greater uneven electron distribution.
2. Stronger induced dipole-dipole attractions between molecules.
3. So, more energy is required to break the attractions between molecules.
4. Hence, boiling and melting point increases.

Question 5

Definition of volatility

Answer 5

The ease at which a liquid turns into a gas.

Question 6

Volatility decreases down the group, because:

Answer 6

1. An increase in the number of electrons.
2. Increases the uneven distribution of electrons.
3. Stronger induced diploe-dipole forces.
4. Hence, the volatility decreases.

Question 7

Reactivity decreases down a group, because:

Answer 7

1. Down the group, the atoms have more electron shells.
2. More shielding of nuclear charge.
3. Less nuclear attraction for incoming electrons.
4. Electrons gained by chlorine more easily than by iodine.
   This means that chlorine has a greater electron affinity for electrons than bromine or iodine.

Question 8

Defintion of electron affinity

Answer 8

Ability of an element to gain an electron.

Question 9

Definition of oxidising power

Answer 9

This is the ability of an atom or species to oxidise another species (take an electron from it).

Question 10

Halide ion sin solution are…

Answer 10

colourless.

Question 11

Chlorine colour in water…

Answer 11

Pale green

Question 12

Chlorine colour in cyclohexane…

Answer 12

Pale green

Question 13

Bromine colour in water…

Answer 13

Orange

Question 14

Bromine colour in cyclohexane…

Answer 14

Orange

Question 15

Iodine colour in water…

Answer 15

Brown

Question 16

Iodine colour in cyclohexane…

Answer 16

Purple

Question 17

Ionic equ, full equ and obs between chlorine and bromine

Answer 17

Cl2(g) + 2Br-(aq) …. Br2(l) + 2Cl-(aq)
Cl2(g) + 2NaBr(aq) …. Br2(l) + 2NaCl(aq)
Obs: pale green to orange (aq or cyclohexane).

Question 18

Ionic equ, full equ and obs between chlorine and iodine

Answer 18

Cl2(g) + 2I-(aq) …. I2(s) + 2Cl-(aq)
Cl2(g) + 2NaI(aq) …. I2(s) + 2NaCl(aq)
Obs: Pale green to brown (water) OR orange to purple (cyclohexane).

Question 19

Ionic equ, full equ and obs between bromide and iodine

Answer 19

Br2(l) + 2I-(aq) …. 2Br(l) + I2(s)
Br2(l) + 2NaI(aq) …. 2NaBr(aq) + I2(s)
Obs: orange to brown (water) OR orange to purple (cyclohexane).

Question 20

The more reactive halogen takes electrons from the less reactive halide (oxidises it). This is because:

Answer 20

Chlorine has less electron shells than Br-/I-.
Chlorine has less sheilding.
Chlorine has more nuclear attraction for incoming electrons.
Chlorine takes electrons from Br-/I-.

Question 21

To prove the reactivity trend, use…

Answer 21

1. Cl2 + Br-
2. Br2 + I-

Question 22

Obs for chloride and acidified silver nitrate…

Answer 22

White precipitate

Question 23

Equ for chloride and acidificed silver nitrate…

Answer 23

Ag+(aq) + Cl-(aq) …. AgCl(s)

Question 24

Obs for bromide and acidified silver nitrate…

Answer 24

Cream precipitate

Question 25

Equ for bromide and acidified silver nitrate

Answer 25

Ag+(aq) + Br-(aq) .... AgBr(s)

Question 26

Obs between iodide and acidified silver nitrate

Answer 26

Yellow precipitate

Question 27

Equ between iodide and acidified silver nitrate

Answer 27

Ag+(aq) + I-(aq) .... AgI(s)

Question 28

Chloride and dilute ammonia solution

Answer 28

AgCl(s) dissolves

Question 29

Bromide and dilute ammonia solution

Answer 29

AgBr(s) remains

Question 30

Bromide and concentrated ammonia solution

Answer 30

AgBr(s) dissolves

Question 31

Iodide and dilute ammonia solution

Answer 31

AgI(s) remains

Question 32

Iodide and concentrated ammonia solution

Answer 32

AgI(s) remains (turns white)

Question 33

Silver fluoride and water

Answer 33

No precipitate formed as silver fluroride is soluble in water

Question 34

Chlorine and water equ

Answer 34

Cl2(g) + H2O(l) ....HClO(aq) + HCl(aq)

Question 35

Explain the change in oxidation numbers for the chlorine and water equ

Answer 35

Chlorine is oxidised as the oxidation number increases from 0 in Cl2 to +1 in HClO. Chlorine is reduced as the oxidation number decreases from 1 in Cl2 to -1 in HCl, so this is reduction. This is an example of a disproportionation reaction.

Question 36

Definition of disproportionation reaction

Answer 36

The same element is both oxidised and reduced.

Question 37

Use for the reaction between water and chlorine

Answer 37

Used to kill bacteria in water. The HClO forms reactive oxygen atoms that destroy bacteria in the water.

Question 38

Chlorine and dliute NaOH(aq) equ

Answer 38

Cl2(g) + 2NaOH(aq) .... NaClO + NaCl(aq) + H2O(l)

Question 39

Explain the change in oxidation numbers for chlorine and dilute NaOH(aq) equ

Answer 39

Chlorine increases in oxidation number from 0 in Cl2 to +1 in NaClO, so chlorine has been oxidised. Chlorine has decreased in oxidation number from 0 in Cl2 to -1 in NaClO, so chlorine has been reduced.

Question 40

Use for the reaction between chlorine and dilute NaOH(aq)

Answer 40

Used in the production of bleach. The active ingredient is NaClO(aq); sodium chlorate (I).