Group 7 (halogens) – chlorine, bromine and iodine

Question 1

• Chlorine is a _______ ______ gas
• Bromine is a ____ ______ liquid
• Iodine is a ____ _____ solid

Answer 1

• yellow - green
• red-brown
• purple - black

Question 2

The melting/boiling points of the halogens _____ as you go ____ the group. This is due to _______ intermolecular forces as the atoms become ________, so more energy is required to overcome these forces.

Answer 2

• increase
• down
• increasing
• larger

Question 3

The halogens react with some metals to form _____________ which are ________________

Answer 3

• ionic compounds
• metal halide salts

Question 4

The halogens ___________ moving down the group, but they still form halide salts with some metals including iron

Answer 4

• decrease in reactivity

Question 5

The rate of reaction is ______ for halogens which are _______________ such as bromine and iodine

Answer 5

• slower
• further down the group

Question 6

The halogens react with non-metals to form ______________________

Answer 6

• simple molecular covalent structures

Question 7

Explain the trend in reactivity in group 7

Answer 7

• The reactivity of non-metals in group 7 decreases as you go down the group.
• As you go down the group, the number of electron shells also increases.
• However, halogen atoms form negative ions when they gain an electron to obtain a full outer shell. The increased distance from the outer shell to the nucleus makes the halogen less reactive.

Question 8

Explain why dilute nitric acid is added and state the observation and the substance responsible.

Answer 8

Observation: White precipitate

The substance responsible: Silver chloride

Explanation: To prevent other precipitates from forming

Question 9

Explain why there is no reaction in experiment 3.

Answer 9

HCl does not form ions

Question 10

Predict the physical state of fluorine at room temperature

Answer 10

Gas

Question 11

Why was there no reaction when iodine was added to sodium bromide solution?

Answer 11

Iodine is less reactive than bromine

Question 12

Name the substance with the brown color that formed when chlorine was added to the potassium iodide solution.

Answer 12

Iodine

Question 13

Some hydrogen gas chloride gas is bubbled into separate samples of water and methylbezene.

State, with a reason, the final colour of the litmus paper in the solution in water

Answer 13

Red - hydrogen ions are present

Question 14

Some hydrogen gas chloride gas is bubbled into separate samples of water and methylbezene.

State, with a reason, the final colour of the litmus paper in the solution in methylbenzene

Answer 14

Blue - no reaction

Question 15

State the observation in the reaction between HCl(g) and ammonia gas and write a chemical equation for the reaction and the result

Answer 15

Observation: White smoke

Chemical equation: NH3 + HCl —-> NH4Cl

result: White precipitate

Question 16

State one change to the magnesium ribbon that could be seen after adding it to solution X

Answer 16

Becomes smaller

Question 17

What does the colour change of the litmus paper show about solution X?

Answer 17

Hydrogen ions present

Question 18

Why does the litmus paper stay blue in solution Y?

Answer 18

No hydrogen ions present

Question 19

Describe a chemical test that the student could do to show that the colourless liquid in step 2 contained chloride ions, Cl-.

Answer 19

test: Add dilute nitric acid, add aqueous silver nitrate

Result: white precipitate forms

Question 20

Potassium bromide can be made by reacting potassium with bromine gas.

Explain why it is difficult to be sure whether the reaction between potassium and bromine gas would be more vigorous than the reaction between sodium and chlorine gas.

Answer 20

• Potassium is more reactive than sodium
• Bromine is less reactive than chlorine