Halogens Flashcards
(16 cards)
What is the order of reducing powers for halides?
F- < Cl- < Br- < I-
Why does reducing power of halides increase down the group?
Because of increasing atomic radius and increasing shielding down the groups
Adding conc. sulphuric acid to a solid halide (NaCl)
NaCl + H₂SO₄ ——> NaHSO₄ +
HCl
- acid-base reaction
- Cl- can’t reduce H₂SO₄
Adding conc. H₂SO₄ to NaBr
NaBr + H₂SO₄ ——> NaHSO₄ + HBr
HBr + H₂SO₄ ——> Br2 + SO ₂ + 2H2O
Redox, Br- reduced (S in) sulphuric acid to sulphur dioxide
Describe and explain the trend in electronegativity
- decreases
- higher atomic radius = bigger atom = more shielding = weaker attraction between nucleus and e- in covalent bond
Describe and explain the trend in boiling point down the group
- increases
- molecules get bigger, more van der waals forces which require more energy to overcome
Oxidising power of halogens
Cl > Br > I
Observations of halides as reducing agents
NaCl- Misty fumes
NaBr- Misty fumes, SO2 (choking gas), Br2 (orangey Brown vapour)
NaI, Misty fumes, SO2 (choking gas), S (yellow powder), H2S (bad egg smell), I2 (purple vapour)
What is disproportionation
Same species has simultaneously has been oxidised and reduced
Displacement reactions of halogens
Cl₂ + 2Br⁻ ——> 2Cl⁻ + Br₂ (yellow solution)
Cl₂ + 2I⁻ ——–> 2Cl⁻ + I₂ (brown solution)
Br₂ + 2I⁻ ———> 2Br⁻ + I₂ (brown solution)
Observations when silver nitrate is added to halides
AgCl- white precipitate
AgBr- cream precipitate
AgI- yellow precipitate
Chlorine reaction to form chlorine water
Cl₂ (g) + H₂O (l) ⇌ HCl (aq) + HClO (aq)
Dissolving Cl₂ in NaOH (cold and dilute)
Cl₂ (g) + 2NaOH ⇌ H₂O + NaCl + NaClO
Chlorine exposed to sunlight
dark Cl₂ + H₂O ⇌ HCl + HClO
sunlight Cl₂ + H₂O ⇌ 2HCl + 1/2 O₂
Why is chlorine added to drinking water?
To remove bacteria
Why is it dangerous to add acidic products to bleach?
System of equilibrium shifts to the left, this produces chlorine which is toxic to humans
