Free Group 17 questions for AS Level Chemistry (9701), part of Inorganic chemistry. Each question has the answer and the marking points an examiner would look for.
Generate a full Group 17 worksheet →All Inorganic chemistry questionsThe hydrogen halides HCl, HBr and HI are compared.
1 The H–X bond energy decreases from HCl to HI.
2 Thermal stability decreases from HCl to HI.
3 HCl decomposes most easily on heating.
Which statements are correct?
Answer: B
Which term is described by this statement?
“Tendency to vaporise; halogen volatility decreases down Group 17.”
Answer: A
Concentrated sulfuric acid is added separately to solid sodium chloride and to solid sodium iodide.
Which row is correct?
| with NaCl | with NaI | |
|---|---|---|
| A | HCl only (steamy fumes) | HI only |
| B | HCl and Cl2 | HI only |
| C | HCl only (steamy fumes) | HI, then I2 and H2S formed |
| D | Cl2 and SO2 | I2 only |
Answer: C
This question is about chlorine, bromine and their compounds.
Explain why hydrogen iodide decomposes more readily on heating than hydrogen chloride.
Chlorine reacts with cold aqueous sodium hydroxide. Write the equation, give the oxidation numbers of chlorine in each product and name this type of reaction.
Write the equation for the reaction with hot sodium hydroxide.
Describe what is seen when concentrated sulfuric acid is added to solid sodium bromide, and explain why it differs from sodium chloride.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | H–I bond weaker the H–I bond is longer M1 so it is weaker and needs less energy to break M1 | 2 |
| (b) | Cl₂ + 2NaOH → NaCl + NaClO + H₂O; −1 and +1; disproportionation Cl₂ + 2NaOH → NaCl + NaClO + H₂O B1 −1 in NaCl and +1 in NaClO B1 disproportionation B1 | 3 |
| (c) | 3Cl₂ + 6NaOH → 5NaCl + NaClO₃ + 3H₂O 3Cl₂ + 6NaOH → 5NaCl + NaClO₃ + 3H₂O B1 | 1 |
| (d) | orange-brown fumes; Br⁻ reduces H₂SO₄ orange/brown fumes of bromine M1 Br⁻ is a strong enough reducing agent to reduce H₂SO₄ but Cl⁻ is not M1 | 2 |
Chlorine reacts with sodium hydroxide.
Write the equation for the reaction with cold dilute NaOH and state the oxidation numbers of chlorine.
| Part | Answer and marking points | Marks |
|---|---|---|
| Cl₂ + 2NaOH → NaCl + NaClO + H₂O; 0, −1, +1 equation B1 0 → −1 and +1 B1 disproportionation B1 | 3 |
This question is about the halogens and their compounds.
Explain the trend in volatility of the halogens down Group 17.
Concentrated sulfuric acid is added separately to solid sodium chloride and to solid sodium iodide. Describe the products in each case and explain the difference.
Chlorine reacts with cold dilute aqueous sodium hydroxide. Write the equation and state the oxidation numbers of chlorine in each product.
Name this type of reaction and explain your answer.
Describe how aqueous silver nitrate followed by aqueous ammonia distinguishes between chloride, bromide and iodide ions.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | volatility decreases; more electrons, stronger instantaneous dipole–induced dipole forces volatility decreases down the group B1 larger molecules with more electrons have stronger instantaneous dipole–induced dipole (London) forces B1 | 2 |
| (b) | NaCl: HCl fumes only; NaI: HI, then SO₂, S, H₂S and purple I₂; I⁻ stronger reducing agent NaCl gives steamy fumes of HCl only B1 NaI gives HI and also SO₂ / S / H₂S with purple vapour / black solid iodine B1 iodide ions are stronger reducing agents than chloride ions B1 they reduce sulfuric acid (S from +6 to lower oxidation states) B1 | 4 |
| (c) | Cl₂ + 2NaOH → NaCl + NaClO + H₂O; −1 and +1 Cl₂ + 2NaOH → NaCl + NaClO + H₂O B1 NaCl: −1 B1 NaClO: +1 B1 | 3 |
| (d) | disproportionation; chlorine both oxidised and reduced disproportionation B1 the same element (chlorine) is simultaneously oxidised (0 to +1) and reduced (0 to −1) B1 | 2 |
| (e) | Cl⁻ white ppt dissolves in dilute NH₃; Br⁻ cream ppt dissolves in conc NH₃; I⁻ yellow ppt insoluble chloride: white precipitate, soluble in dilute ammonia B1 bromide: cream precipitate, soluble in concentrated ammonia B1 iodide: yellow precipitate, insoluble in concentrated ammonia B1 | 3 |
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