A summary of topic 4, organised so the notes are easy to understand. The notes are on slides, so they can be printed out and used as revision cards or posters, for revision on the go. The notes cross-reference the specification so it is easy to see where each bit of information has come from. They ...
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
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller laurelgracefell. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.
