Group 7 Test for halides (silver nitrate):
Reactivity ↓ down group (↑ shells = ↓ attraction) NaX + AgNO3 →AgX + NaNO3
MPT & BPT ↑ down group (↑ london forces) Ppts: AgCl = white & darkens in light
Electronegativity ↓ down group (↑ shells = ↓ attraction) AgBr = cream & darkens in light
Organic solubility ↑ down group (↑ london forces) AgI = yellow
Water solubility ↓ down group (↓ electronegativity) Ammonia solubility: AgCl = dissolves in conc & dil
Colours: (test for halogens) AgBr = dissolves in conc
Halogen At room temp In aq solution In organic solution AgI = doesn't dissolve
Reducing power:
F Pale yellow gas x x MX + H2SO4 → HX + MHSO4
Cl Pale green gas colourless colourless
- When heated w/ conc H2SO4 halides act as reducing agents (loose
e-, donate e- to another species)
Br Orange/brown liquid orange orange/red - X- loses an e- when it reduces H 2SO4
- Down group = easier to lose an e- due to ↑ radii & ↑ shielding ∴ I-
I Black solid brown pink/violet
ions most reactive
Redox reactions of halogens w/ halides - ∴ I- reduce H2SO4 further
- 2NaBr + Cl2 →2NaCl + Br2 (goes orange in aq & org solvent) Method = add halide + H2SO4 & observe gases leaving the tube.
Cl2 + 2Br- →2Cl- + Br2 Test for HX gases w/ ammonia (explained later)
- 2NaI + Cl2 →2NaCl + I2 (goes brown in aq, pink in org solvent) 1. Cl-
Cl2 + 2I- →2Cl- + I2 H+ + Cl- → HCl (HCl - white misty fumes, white smoke-y fumes w/ ammonia)
- 2NaI + Br2 →2NaBr + I2 (goes brown in aq, pink in org solvent) 2. Br-
Br2 + 2I- →2Br- + I2 H+ + Br- → HBr (HBr - white misty fumes, white smoke-y fumes w/ ammonia)
Disproportionation: H2SO4 + 2H+ + 2Br- → Br2 + SO2 + 2H2O (Br2 = orange fumes,
SO2 = colourless choking fumes)
1. Cl2 + water to kill bacteria
Cl2 (aq) + H2O(l) → HClO(aq) + HCl(aq) 3. I-
0 +1 -1 H+ + I- → HI (HI - white misty fumes, white smoke-y fumes w/ ammonia)
2. Bleach (NaClO) made from Cl2 + cold NaOH H2SO4 + 2H+ + 2I- → I2 + SO2 + 2H2O (I2 = orange fumes,
SO2 = colourless choking fumes)
Cl2 (aq) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H 2O(l)
H2SO4 + 6H+ + 6I- → 3I2 + S + 4H2O (S = yellow solid)
0 -1 +1
H2SO4 + 8H+ + 8I- → 4I2 + H2S + 4H2O (H2S = colourless gas, egg smell)
Reactions w/ alkali’s:
Hydrogen halides:
3. Cold, strong alkalis Colourless, soluble gases due to polar H-X
X2 (aq) + 2MOH(aq) → MX(aq) + MXO(aq) + H 2O(l) W/ water, HX(g) + H2O(l) → H3O+(aq) + X-(aq)
0 -1 +1 W/ ammonia, HX(g) + NH3(g) → NH4X(aq) [salt]
4. Hot, strong alkalis HX test (used in reducing power test)
3X2 (aq) + 6MOH(aq) → 5MX(aq) + MXO 3(aq) + 3H2O(l) - Glass rod dipped in ammonia
0 -1 +5 - If it comes into contact w/ HX, white smoke from solid NH4X
Reactivity ↓ down group (↑ shells = ↓ attraction) NaX + AgNO3 →AgX + NaNO3
MPT & BPT ↑ down group (↑ london forces) Ppts: AgCl = white & darkens in light
Electronegativity ↓ down group (↑ shells = ↓ attraction) AgBr = cream & darkens in light
Organic solubility ↑ down group (↑ london forces) AgI = yellow
Water solubility ↓ down group (↓ electronegativity) Ammonia solubility: AgCl = dissolves in conc & dil
Colours: (test for halogens) AgBr = dissolves in conc
Halogen At room temp In aq solution In organic solution AgI = doesn't dissolve
Reducing power:
F Pale yellow gas x x MX + H2SO4 → HX + MHSO4
Cl Pale green gas colourless colourless
- When heated w/ conc H2SO4 halides act as reducing agents (loose
e-, donate e- to another species)
Br Orange/brown liquid orange orange/red - X- loses an e- when it reduces H 2SO4
- Down group = easier to lose an e- due to ↑ radii & ↑ shielding ∴ I-
I Black solid brown pink/violet
ions most reactive
Redox reactions of halogens w/ halides - ∴ I- reduce H2SO4 further
- 2NaBr + Cl2 →2NaCl + Br2 (goes orange in aq & org solvent) Method = add halide + H2SO4 & observe gases leaving the tube.
Cl2 + 2Br- →2Cl- + Br2 Test for HX gases w/ ammonia (explained later)
- 2NaI + Cl2 →2NaCl + I2 (goes brown in aq, pink in org solvent) 1. Cl-
Cl2 + 2I- →2Cl- + I2 H+ + Cl- → HCl (HCl - white misty fumes, white smoke-y fumes w/ ammonia)
- 2NaI + Br2 →2NaBr + I2 (goes brown in aq, pink in org solvent) 2. Br-
Br2 + 2I- →2Br- + I2 H+ + Br- → HBr (HBr - white misty fumes, white smoke-y fumes w/ ammonia)
Disproportionation: H2SO4 + 2H+ + 2Br- → Br2 + SO2 + 2H2O (Br2 = orange fumes,
SO2 = colourless choking fumes)
1. Cl2 + water to kill bacteria
Cl2 (aq) + H2O(l) → HClO(aq) + HCl(aq) 3. I-
0 +1 -1 H+ + I- → HI (HI - white misty fumes, white smoke-y fumes w/ ammonia)
2. Bleach (NaClO) made from Cl2 + cold NaOH H2SO4 + 2H+ + 2I- → I2 + SO2 + 2H2O (I2 = orange fumes,
SO2 = colourless choking fumes)
Cl2 (aq) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H 2O(l)
H2SO4 + 6H+ + 6I- → 3I2 + S + 4H2O (S = yellow solid)
0 -1 +1
H2SO4 + 8H+ + 8I- → 4I2 + H2S + 4H2O (H2S = colourless gas, egg smell)
Reactions w/ alkali’s:
Hydrogen halides:
3. Cold, strong alkalis Colourless, soluble gases due to polar H-X
X2 (aq) + 2MOH(aq) → MX(aq) + MXO(aq) + H 2O(l) W/ water, HX(g) + H2O(l) → H3O+(aq) + X-(aq)
0 -1 +1 W/ ammonia, HX(g) + NH3(g) → NH4X(aq) [salt]
4. Hot, strong alkalis HX test (used in reducing power test)
3X2 (aq) + 6MOH(aq) → 5MX(aq) + MXO 3(aq) + 3H2O(l) - Glass rod dipped in ammonia
0 -1 +5 - If it comes into contact w/ HX, white smoke from solid NH4X
