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A2 Level · Chemistry 6 (IAL) WCH16

Advanced Inorganic & Organic Chemistry Core Practicals

Revise Advanced Inorganic & Organic Chemistry Core Practicals for Chemistry 6 (IAL) WCH16 (A2 Level) — revision notes, 14 practice questions and instant AI marking.

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Edexcel IAL Chemistry — Core Practicals

Advanced Inorganic & Organic
Chemistry Core Practicals

The Big Idea: Five practicals, one skill underneath all of them — using colour changes, precipitates, and precise measurements to work out exactly how much of something is present, or exactly what something is, by controlling every variable so the only thing that changes is the chemistry you're trying to observe.

Summary — What This Chapter Covers

Core Practical 13a: Redox titration between iron(II) and manganate(VII) — self-indicating, no indicator needed.
Core Practical 13b: Redox titration between iodine and thiosulfate — uses starch as an indicator near the end point.
Core Practical 12: Preparing a transition metal complex — tetraamminecopper(II) sulfate crystals — and calculating percentage yield.
Core Practical 15: Qualitative analysis — identifying unknown positive ions (Group 2 metals, ammonium), negative ions (halides, hydroxide, carbonate, sulfate), and organic functional groups (alkenes, alcohols, carbonyls, carboxylic acids).
Core Practical 16: Preparing aspirin from salicylic acid, then purifying it by recrystallisation and checking its purity with a melting point test.

Core Practical 13a

Redox Titration — Iron(II) & Manganate(VII)

Think of a titration as a chemical "weighing scale." You know the exact concentration of one solution (the one in the burette), and you slowly add it to a known volume of the other solution until the reaction is exactly complete. The volume you needed tells you how much of the unknown substance was there.

In a redox titration, instead of an acid neutralising a base, you have an oxidising agent reacting with a reducing agent — electrons are being transferred from one species to the other. The clever part is that many transition metal ions change colour when they change oxidation state, so you often don't even need to add a separate indicator — the reaction indicates itself.

Why Sulfuric Acid, and Nothing Else?

In this titration, manganate(VII) ions (MnO₄⁻) are the oxidising agent — they get reduced to Mn²⁺. Iron(II) is the reducing agent — it gets oxidised to Fe³⁺. This reaction only works in acidic conditions, so excess acid is added to the iron(II) solution before you even start titrating.

But you can't just grab any acid off the shelf. The acid has one job: provide H⁺ ions, and stay completely out of the redox chemistry. Dilute sulfuric acid is the only one that does this cleanly:

Acid	Why it's rejected
Hydrochloric acid	Chloride ions get oxidised to chlorine by the manganate(VII) — it reacts when it shouldn't.
Nitric acid	It's an oxidising agent itself — it could oxidise the iron(II) directly, ruining the titre.
Ethanoic acid	It's a weak acid — not enough H⁺ ions are released to keep the solution acidic enough.
Concentrated sulfuric acid	Concentrated (not dilute) sulfuric acid can act as an oxidising agent too.

The pattern to remember A "safe" acid for a redox titration must be (1) strong enough to be fully acidic, and (2) redox-inert — meaning its own ions can't be oxidised or reduced under the reaction conditions. Dilute sulfuric acid ticks both boxes; nothing else on a typical exam's list does.

Spotting the End Point

every pale pink

Core Practical 13b

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Also in the full note

Redox Titration — Thiosulfate & Iodine
Preparing a Transition Metal Complex
Qualitative Analysis of Inorganic & Organic Unknowns
Aspirin Preparation
What to Memorise
Concepts Checklist
Exam Tips — Common Mistakes & Mark-Scheme Traps
Building and Balancing the Equation

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