Inorganic 1 Section 2 - Unit 10: Halogens Flashcards
State the equation for the reaction between chlorine and water (1 mark)
- Cl2 + H2O → HOCl + HCl
When a pool has a pH of over 7.0, explain how adding chlorine to water affects the equilibrium (2 marks)
- Alkaline ions react with acid
- So equilibrium shifts to the right
Explain why chlorine is used to kill bacteria in swimming pools, even though chlorine is toxic (2 marks)
- Only used in small amounts
- Health benefits outweigh the risk
Which substance reacts most rapidly to produce a silver halide precipitate with acidified silver nitrate?
- CH3l
Explain why chlorine has a lower boiling point than bromine (1 mark)
- Chlorine is smaller than bromine
- Cl2 has weaker intermolecular forces
State how you could tell the difference between AgBr and AgI (3 marks)
- Concentrated ammonia
- Cream solid dissolves
- Yellow solid does not dissolve
Describe fluorine (1)
- Pale yellow gas
Describe chlorine (1)
- Greenish gas
Describe bromine (2)
- Red liquid
- Gives off brown/orange poisonous fumes
Describe iodine (2)
- Shiny grey solid
- Purple gas
Explain why melting and boiling point increases down the halogen group (3 marks)
- Down the group, more electrons
- So larger VDW
- So more energy required to break the forces
Role of H₂SO₄ when reacting with NaF and NaCl (1 mark)
- Acid
Role of H₂SO₄ when reacting with NaBr and NaI (2 marks)
- Acid in first step
- Then oxidising agent
Appearance of HI (1 mark)
- White steamy fumes
Appearance of SO₂ (1 mark)
- Colourless acidic gas
Appearance of H₂S (1 mark)
- Gas with bad egg smell
Equation for reaction of NaF with H₂SO₄ (1 mark)
NaF (s) + H₂SO₄ (l) —> NaHSO₄ (s) + HF (g)
Observation for reaction of NaF with H₂SO₄ (1 mark)
White steamy fumes of HF
Equation for reaction of NaCl with H₂SO₄ (1 mark)
NaCl (s) + H₂SO₄ (l) —> NaHSO₄ (s) + HCl (g)
Observation for reaction of NaCl with H₂SO₄ (1 mark)
White steamy fumes of HCl
Explain why redox reactions do not occur with NaF and NaCl with H₂SO₄ (2 marks)
- F- and Cl- are not strong enough reducing agents
- So cannot reduce the S in H₂SO₄
Equation for acid-base step of reaction of NaBr with H₂SO₄ (1 mark)
NaBr (s) + H₂SO₄ (l) —> NaHSO₄ (s) + HBr (g)
Equation for redox step of reaction of NaBr with H₂SO₄ (1 mark)
2H+ + 2Br- + H₂SO₄ –> Br₂ + SO₂ + 2H₂O
Overall equation for reaction of NaBr with H₂SO₄ (1 mark)
2NaBr + 3H₂SO₄ –> 2NaHSO₄ + Br₂ + SO₂ + 2H₂O
Observations for reaction of NaBr with H₂SO₄ (3 marks)
- White steamy fumes of HBr
- Orange fumes of bromine
- Colourless, acidic gas SO₂
Equation for acid-base step of reaction of NaI with H₂SO₄ (1 mark)
NaI(s) + H₂SO₄ (l) –> NaHSO₄ (s) + HI(g)
State the redox step for the reaction of NaI with H₂SO₄, when SO₂ is given off (1 mark)
2 H+ + 2 I- + H₂SO₄ –> I₂ (s) + SO₂ (g) + 2 H₂O(l)
State the redox step for the reaction of NaI with H₂SO₄, when S is produced (1 mark)
6 H+ + 6 I- + H₂SO₄ –> 3 I₂ (s) + S (s) + 4 H₂O (l)
State the redox step for the reaction of NaI with H₂SO₄, when H₂S is given off (1 mark)
8 H+ + 8 I- + H₂SO₄ –> 4 I₂ (s) + H₂S(g) + 4 H₂O(l)
Observations for reaction of NaI with H₂SO₄ (5 mark)
- White steamy fumes of HI
- Black solid and purple fumes of iodine
- Colourless acidic gas of SO₂
- Yellow solid of sulfur
- H₂S gas with bad egg smell
State the equation for the reaction of chlorine with water in sunlight (1 mark)
2Cl₂ + 2H₂O –> 4HCl + O₂
State the equation for the reaction of chlorine with water (1 mark)
Cl₂ + H₂O –> HCl (aq) + HClO (aq)
State the observation when universal indicator is added to the reaction of chlorine with water (2 marks)
- First turns red due to acidity of both reaction products
- Then turns colourless as the HClO bleaches the colour
