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Flashcards

8.2 The halogens

Urvi B Chemistry A level English 49 cards

Cards in this deck (49)

  1. 1On earth halogens occur as what? Give examples.Halide ions (Cl-, Br- and I-)
  2. 2What group are the halogens?Group 7
  3. 3At RTP all the halogens exist as what molecules?Diatomic molecules
    X2
  4. 4In their solid states the halogens from lattices with what structures?Simple molecular structures
  5. 5What is appearance and state at RTP of F2pale yellow
    gas
  6. 6What is appearance and state at RTP of Cl2pale green
    gas
  7. 7What is appearance and state at RTP of Br2red-brown
    liquid
  8. 8What is appearance and state at RTP of I2shiny grey-black
    solid
  9. 9What is appearance and state at RTP of At2never been seen
  10. 10Explain the trend down the halogens (group 7).- More electrons
    - Stronger London forces
    - More energy required to break the intermolecular forces
    - Boiling point increases
  11. 11What is the outer-shell configurations of the halogens?s2, p5
  12. 12What reactions are the most common type of reaction of the halogens?Redox reactions
  13. 13What happens in a redox reaction with an halogen?halogen atom reduced - gain one electron to form a 1- halide ion with electronic configuration of nearest noble gas
  14. 14Is halogen an oxidising or reducing agent and why?Oxidising agent because it has oxidised another species
    (another species loses electrons to halogen atoms which is oxidised)
  15. 15What do the results of the displacement reactions show?Shows reactivity of the halogens decreases down the group
  16. 16How do you carry out the displacement reaction with test tubes? Give examples- solution of each halogen is added to aqueous solutions of the other halides
    e.g. a solution of chlorine (Cl2) is added to two aqueous solutions containing bromine (Br-) and Iodine (I-) ions
  17. 17What happens if the halogen added is more reactive than the halide present?- a reaction takes place, the halogen displacing the halide from solution
    - the solution changes colour
  18. 18What can you add to tell apart the solutions of iodine and bromine because they appear a similar orange-brown colour?And why would you add it?Organic non-polar solvent such as cyclohexane
    Non-olar halogens dissolve more readily in cyclohexane
  19. 19What does Cl2 look like in water and cyclohexane?Water - pale green
    Cyclohexane - pale green
  20. 20What does Br2 look like in water and cyclohexane?Water - orange
    Cyclohexane - orange
  21. 21What does 12 look like in water and cyclohexane?Water - brown
    Cyclohexane - violet
  22. 22Give the equation and colour when the halogen Cl2(aq) is added to Br-(aq) (halide).Orange colour from Br2 formation
    Cl2(aq) + 2Br-(aq) → 2Cl-(aq) +Br2(aq)
  23. 23Give the equation and colour when the halogen Cl2(aq) is added to I-(aq).Violet colour from I2 formation
    Cl2(aq) + 2I-(aq) → 2Cl-(aq) + I2(aq)
  24. 24Give the equation and colour when Br2(aq) is added to Cl-(aq).No reaction (Cl- is more reactive than Br)
  25. 25Give the equation and colour when the halogen Br2(aq) is added to I-(aq).Violet colour from I2 formation
    Br2(aq) + 2I-(aq) → 2Br-(aq) + I2(aq)
  26. 26When I2(aq) is added to Cl- or Br- is there a reaction?No
  27. 27What can you tell from the halogen displacement reactions? (results)- Chlorine reacts with both Br- and I-
    - Bromine has reacted with I- only
    - Iodine has not reacted at all
  28. 28Cl2(aq) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq) Give the ionic equation.Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq)
  29. 29Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq) In terms of oxidation number describe what has been oxidised and what has been reduced.- 2 Br in 2Br-
    Each Br increases by +1
    Total increase = +2
    - 2 Cl in Cl2
    Each Cl decreases by -1
    Total decrease = -2
  30. 30What happens to fluorine?Pale yellow gas
    Reacts with almost any substance that it comes in contact with
  31. 31What happens to astatine?Radioactive and decays rapidly
    Least reactive halogen
  32. 32In redox reactions, halogens react by _______ electrons. Down the group, the tendency to gain an electron _________ and the halogen becomes less reactive.Gaining
    Decreases
  33. 33Explain the trend in reactivity of the halogens.- Atomic radius increases
    - More inner shells so shielding increases
    - Less nuclear attraction to capture an electron from another species
    - Reactivity decreases
  34. 34Which of the strongest oxidising agent of the halogens?Fluorine - gainss electrons from other species more rapidly than the other halogens
  35. 35What is disproportionation?Redox reaction in which the same element is most oxidised and reduced.
  36. 36What can chlorine be used for?Water purification
    Disinfectant
  37. 37What reaction takes place when clorine is added to water?Disproportionation reaction
  38. 38What is the equation for adding chlorine to water?Cl2(aq) + H2O(l) → HClO(aq) + HCl(aq)
  39. 39Cl2(aq) + H2O(l) → HClO(aq) + HCl(aq) What has been oxidised and what has been reduced in the reaction?Cl - reduction from 0 to -1 (in HCl)
    Cl- oxidation from 0 to +1 (in HClO)
  40. 40What are the two products from adding chlorine and water together? How are the bacteria killed?Chloric(I) acid, HClO and hydrochloric acid, HCl.
    Bacteria killed by chloric(I) acid and chlorate(I) ions, ClO-
  41. 41Cloric(I) acid can act as a weak bleach. How can you demonstrate this?- Adding some indicator solution to a solution of chlorine in water
    - Indicator first turns red from the presence of the two acids
    - Colour than disappears as bleaching action of chloric(I) acid takes place
  42. 42Why is the reaction of chlorine with water limited?Low solubility of chlorine in water
  43. 43If the water contains dissolved what? Much much more clorine dissolves.Sodium hydroxide
  44. 44Write the equation for the reaction of chlorine with sodium hydroxide forming sodium chlorate(I), sodium chloride and water.Cl2(aq) + 2NaOH(aq) → NaClO(aq) + NaCl(aq) + H2O(l)
  45. 45Cl2(aq) + 2NaOH(aq) → NaClO(aq) + NaCl(aq) + H2O(l) What has been oxidised and what has been reduced?Cl2 - 0 to -1 (NaCl) reduction
    Cl2- 0 to +1 is (NaClO) oxidation
  46. 46Cl2(aq) + 2NaOH(aq) → NaClO(aq) + NaCl(aq) + H2O(l) What type of reaction is this?Disproportionation reaction
  47. 47What do you get more of when you react chlorine with sodium hydroxide rather than water?Larger concentration of chlorate(I), ClO- ions
  48. 48What are the benefits and risks of chlorine use? (5)- Ensuring water is fit to drink and bacteria are killed
    - Chlorine is a toxic gas - respiratory irritant in small concentrations
    - Chlorine in drinking water can react with organic hydrocarbons such as methane. Chlorinated hydrocarbons are formed - cancer.
    - Quality of drinking water would be comprimised. Diseases such as typhoid and cholera might break out.
    - Can be used after a natural disaster - life-saving (safe water supply)
  49. 49What happens in a precipitation reaction with aqueous silver ions? And give the general equation (X-(aq) represents aqueous solution of any halide).Aqueous halide ions react with aqueous silver ions to form a precipitates of silver halides
    Ag+(aq) + X-(aq) → AgX(s)

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A level Chemistry (Module 3: Periodic table and energy) Flashcards on 8.2 The halogens, created by Urvi B on 04/01/2018.
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