Topic 10: Group 7 The Halogens Flashcards
All halogens are…
Diatomic X2
Reactions of Halogens with their ions (KX) table
KCl KBr KI
Cl2 X orange sol’n brown sol’n
Br2 X X brown sol’n
I2 X X X
Equation of Cl2 with KBr and colour change
Cl2 + 2KBr —> 2KCl + Br2 (turns orange) Bromine produces turns it orange
Br2 and I- and colour change
Br2+ 2KI —> 2KBr + I2 (turns brown) Iodine produced turns it brown
Oxidising power down g7
Decreases down group
Formation of bleach
2NaOH + Cl2 —> NaClO (bleach (sodium chlorate)) + NaCl + H2O
Chloride oxidised/ reduced in formation of bleach
Disproportionation reaction - Both oxidised and reduced
Chorine and water reaction
Normal - disproportionation reaction
Cl2 + H2O <===> HClO + H2O
in UV light:
2Cl2 + 2H2O —> 4HCl + O2
Chlorine added to water even though toxic
Benefit outweighs the risk - kills bacteria
Halogens reducing power
Decreases down group, atomic radii decreases, stronger att’n to nucleus
NaCl/NaF with sulphuric acid equ’n and appearance
NaCl + H2SO4 —> NaHSO4 + HCl
STEAMY WHITE FUMES!!
(NOT REDOX)
NaBr with sulphuric acid eq’n and appearance
NaBr + H2SO4 —> NaHSO4 + HBr
STEAMY WHITE FUMES - not redox
2HBr + H2SO4 —> Br2 + SO2 +2H2O
brown fumes - Br produces - redox
NaI with sulphuric acid eq’n and appearance
NaI + H2SO4 —> NaHSO4 + HI
STEAMY WHITE FUMES - not redox
2HI + H2SO4 —> I2 + SO2 +2H2O black solid (I2) - Br produces - redox
6HI + SO2 —> H2S + 3I2 + 2H2O
toxic, smells rotten (H2S) redox again
Halide tests general
Halide containing solution + HNO3 (removes unwanted ions like CO3^2-) + AgNO3
Halide tests equation
Ag+ + X- —> AgX (ppt)
