Group 7

Question 1

What group are the halogens in? Why?

Answer 1

Group 7 because they have 7 outer shell

electrons.

Question 2

What is the colour and state of chlorine at room

temperature?

Answer 2

Pale green gas

Question 3

What is the colour and state of bromine at room

temperature?

Answer 3

Red-brown liquid

Question 4

What is the colour and state of iodine at room

temperature?

Answer 4

Black solid

Question 5

Why are the halogens at different states at room

temperature? What is the trend down the group?

Answer 5

At room temperature, chlorine is gaseous,
bromine is liquid and iodine is solid because they
have different melting and boiling points. As you
go down the group, melting and boiling point
increases.

Question 6

What state would you expect the halogens fluorine

and astatine to be at room temperature?

Answer 6

Fluorine is above chlorine so should have a boiling point
lower than chlorine. This means it would be a gas at room
temperature.

Astatine is below iodine in group 7 so should have a higher
melting point than iodine. Therefore you can predict that it
would be a solid at room temperature.

Question 7

Why does melting and boiling point increase down Group 7?

Answer 7

The molecules get bigger down the group so there are more intermolecular forces to overcome during melting / boiling so more energy is required.

Question 8

What is the chemical test for chlorine?

Answer 8

Damp litmus paper placed into a test
tube of gas. If chlorine is present, the
litmus paper will turn red then white due
to the bleaching effect of chlorine

Question 9

Halogens are diatomic. What does this mean?

Answer 9

They form molecules consisting of 2
atoms

E.g: Cl2 , Br2…

Question 10

What charge does a halide ion carry? Why?

Answer 10

• 1
  e. g. Cl-, Br-…

They gain one electron to have a stable
electron configuration.

Question 11

What is produced when a halogen reacts with a

metal?

Answer 11

Metal halide salt

Question 12

Write a balanced symbol equation for the reaction

between bromine and sodium

Answer 12

Br2 + 2Na → 2NaBr (check google if unsure)

Question 13

Write a balanced symbol equation for the reaction

between chlorine and calcium

Answer 13

Cl2 + Ca → CaCl2 (check google if unsure)

Question 14

Predict the product of the reaction between

magnesium and fluorine

Answer 14

Magnesium fluoride (MgF2)

Question 15

Write a word equation for the reaction between

iodine and potassium

Answer 15

Iodine + potassium → Potassium iodide.

Remember: the ion of a halogen ends
with -ide.

Question 16

Describe the trend in reactivity of the halogens. How

does this affect the rate of reaction?

Answer 16

Reactivity decreases down group 7.

Rate of reaction decreases down group 7

Question 17

What is formed when hydrogen reacts with a

halogen?

Answer 17

Hydrogen halides

e.g. HCl, HBr…

Question 18

Chlorine reacts with hydrogen in the presence of

sunlight but bromine requires a flame. Why?

Answer 18

Reactivity decreases down the group so
bromine requires more energy for the
reaction to occur

Question 19

What is formed when a hydrogen halide dissolves in

water?

Answer 19

An acidic solution. Hydrogen ions

dissociate, making the solution acidic.

Question 20

Write a balanced symbol equation for the reaction

between hydrogen and chlorine

Answer 20

H2 + Cl2 → 2HCl (check if unsure)

Question 21

Predict the product of the reaction between

hydrogen and fluorine

Answer 21

Hydrogen fluoride (HF)

Question 22

When does a halogen displacement reaction occur?

Answer 22

When a more reactive halogen displaces
a less reactive halogen from an aqueous
solution of its halide.

Question 23

Why will halide ions A only be displaced by halogen

B if B is above A in group 7?

Answer 23

The most reactive halogen (B) will displace the
less reactive halogen (A) to become part of the
ionic compound. Reactivity increases as you go
up the group so B must be higher in group 7 to
be more reactive than A

Question 24

Which halogens can chlorine displace from an

aqueous ionic solution?

Answer 24

Chlorine can displace any halogens
below it in group 7. It will displace iodine
and bromine.

Question 25

Which halogens can’t be displaced from an aqueous

ionic solution by bromine?

Answer 25

Bromine can’t displace any halogens
above it in group 7. These are chlorine
and fluorine.

Question 26

Why can iodine not displace chlorine or bromine

from an aqueous ionic solution?

Answer 26

Because reactivity decreases down the group
and iodine is below chlorine and bromine
group 7. Displacement will only occur if iodine
is more reactive than the halogen in the ionic
compound.

Question 27

Write the word equation for the reaction between

chlorine and potassium bromide

Answer 27

Chlorine + potassium bromide → potassium chloride + bromine

Question 28

Write the word equation for the reaction between

bromine and calcium chloride

Answer 28

No reaction will occur because bromine
is less reactive than chlorine so chlorine
won’t be displaced.

Question 29

Write the balanced symbol equation for the reaction
that takes place between bromine and potassium
iodide

Answer 29

Br2 + 2KI → I2 + 2KBr (check google if unsure)

Question 30

Which halogens would you expect astatine to be

able to displace?

Answer 30

None of them. It is at the bottom of group

7 so has the lowest reactivity.

Question 31

Why does reactivity decrease down group 7?

Answer 31

As you go down group 7, the outer shell is further
from the nucleus and electron shielding increases.
Attraction between the nucleus and outer electrons
decreases so it is harder for the atom to gain an
electron meaning reactivity decreases.

Question 32

What colours are solutions of chlorine, bromine and

iodine?

Answer 32

Chlorine water - colourless
Bromine water - orange
Iodine solution - brown

Question 33

What would you observe when chlorine is added to

potassium bromide?

Answer 33

Cl2 + 2KBr → Br2 + 2KCl

Colour change from colourless (due to Cl2) to orange (due to Br2).

Question 34

What is a redox reaction?

Answer 34

A reaction where oxidation and reduction

take place at the same time.

Question 35

Are halogen displacement reactions redox

reactions? Explain your answer

Answer 35

Yes because the halide ion is oxidised (loses an
electron) to form a halogen atom and the halogen
is reduced (gains an electron) to form a halide
ion.

Question 36

Write the two half equations for the reaction between
chlorine and potassium bromide, stating which is
reduction and which is oxidation

Answer 36

Overall equation: Cl2 + 2KBr → Br2 + 2KCl
Reduction: Cl + 2e- → 2Cl2
Oxidation: 2Br- → Br + 2e

Question 37

Bromine reacts with potassium iodide. What is

reduced and what is oxidised?

Answer 37

Bromine is reduced to bromide ions.

Iodide ions are oxidised to iodine.