MYP Chemistry: Salts & Their Preparation — Answered

A salt is the ionic compound formed when the hydrogen ion of an acid is replaced by a metal ion or ammonium ion, produced through neutralisation, acid-metal, acid-carbonate or precipitation reactions. In MYP Chemistry you classify salts mainly by solubility — soluble or insoluble — because that decides your preparation method.

There are three core methods: titration, used when both reactants and the product salt are soluble (a strong acid plus an alkali); the excess-solid method, used when one reactant is an insoluble metal, oxide or carbonate; and precipitation, used when the target salt itself is insoluble.

Check the solubility of the salt itself first. If it's soluble and both reactants dissolve, use titration. If it's soluble but one reactant is a solid metal, oxide or carbonate, use the excess-solid method. If the salt is insoluble, mix two soluble solutions and filter the precipitate.

A soluble salt dissolves fully and must be separated by evaporation followed by crystallisation. An insoluble salt forms as a solid precipitate immediately and is separated by filtration instead. Mix these up on paper — describing filtration for a soluble salt, say — and you'll lose marks for a genuine conceptual error, not a slip.

Start by identifying whether the salt is soluble or insoluble — this decides your method: titration, excess solid, or precipitation. State the reactants, write a balanced equation with state symbols, name the products, and justify each step using solubility rules rather than just describing the practical from memory.

Write the full balanced equation first, split every soluble ionic compound into its separate ions, then cancel any spectator ions appearing unchanged on both sides. What's left — usually two or three ions forming a solid or water — is your ionic equation, and it needs state symbols to be complete.

Three errors account for most lost marks: forgetting to write 'excess' when a solid reactant is added, describing evaporation for what should be a filtered precipitate, and leaving out state symbols in the final equation. Each looks minor on the page but signals a genuine gap to whoever's marking it.

Expect 'outline' or 'describe' for method steps, 'construct' when you need a balanced equation, 'identify' for naming the correct technique, and 'explain' or 'justify' when you must give the scientific reasoning — for instance why excess solid is used, or why a precipitate forms instantly.

You need four techniques: filtration to remove excess solid or collect a precipitate, evaporation to concentrate a soluble salt solution, crystallisation to grow pure crystals from a saturated solution, and washing/drying to remove impurities from a precipitate. Name the correct one for each stage — don't just write 'purify it.'

Salts practicals are most often assessed against Criterion B, Inquiring and designing, for planning a safe and logical method, and Criterion C, Processing and evaluating, for handling crystal yield and error sources. Criterion A, Knowing and understanding, covers the theory questions on solubility and equations that usually follow.

Safety isn't a separate MYP criterion — it's folded into Criterion B, where you're expected to identify and justify precautions: safety glasses, adding acid to water rather than the reverse, and never heating a sealed vessel while a carbonate-acid reaction is producing gas. A method that skips hazards genuinely loses marks.

MYP treats salts descriptively — naming methods, writing equations, choosing techniques by solubility. According to the IB, the current DP Chemistry guide, first examined in 2025, revisits the same acid-base chemistry with far more quantitative depth under the Reactivity strand, adding titration calculations and equilibrium concepts your child won't meet until Diploma years.

Practice questions and topic-specific worksheets do more for this topic than re-reading notes, because salts questions reward quick method recognition under time pressure. Look for resources pairing short Revision Notes on solubility rules with Topical Worksheets your child can mark against a real markscheme — that's what builds exam speed.

Yes — it's one of the most common sticking points in MYP 4-5 Chemistry because it mixes practical technique with abstract ionic theory in a single topic. Most students who struggle are missing the solubility rules, not the reactions themselves; once those are solid, method choice usually clicks within a lesson or two.