Pearson International A Level Chemistry Core Practical 14: Prepare a transition metal complex

This core practical is part of Pearson's practical-learning programme. The method below is one defensible implementation, not a confidential instruction sheet. Centres may adapt equipment while preserving the scientific purpose, controls, measurements and safety requirements.

Aim and scientific principle

Prepare and isolate a coordination compound, then assess purity and yield from controlled synthesis and purification.

Begin by translating the title into a testable question. Identify what is deliberately changed, what is measured directly, what is calculated and what must remain controlled. Predict a relationship only after naming the mechanism. A prediction without a reason is weak; a reason without measurable variables cannot guide a practical design.

Apparatus and setup

Use reaction vessel, measured metal salt and ligand solutions, heater or ice bath, filtration apparatus, wash solvent, drying equipment and balance. Select every measuring instrument by range and resolution, not by name alone. Draw a labelled scientific setup that shows the working geometry and exactly where readings are taken. Include a control or blank when it distinguishes the target effect from drift, contamination or background response.

Before collecting results, check zero readings, calibration, leaks, alignment or sterility as relevant. Record the instrument resolution beside the first raw-data table. If a digital device displays more digits than its underlying accuracy supports, do not treat every digit as equally certain.

Method

1. Measure stoichiometric reactants and control pH, temperature and order of addition.
2. Allow complex formation or crystallisation under the specified conditions.
3. Collect product by filtration, wash with small cold portions and dry to constant mass.
4. Calculate theoretical and percentage yield, and record colour or analytical evidence cautiously.

Plan the analysis before starting. This reveals whether an additional measurement is needed for a derived quantity and prevents a completed experiment from lacking a mass, length, concentration, background or calibration value. A method should be detailed enough for another trained student to reproduce, while avoiding decorative steps that do not affect validity.

Variables and controls

• Independent variable: reaction or crystallisation condition when investigated.
• Dependent variable: product mass, yield, colour or purity evidence.