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CBSE Class 12 chemistry practical, Inorganic preparation · Preparation of compounds

Source: CBSE Class 12 chemistry practical syllabus · use your school laboratory manual (NCERT Lab Manual where your school uses it).

Preparation of potassium trioxalatoferrate(III) (Class 12 chemistry practical)

You combine ferric ion with oxalate to form a coordination compound and crystallise green needles.

Masses and volumes are in your manual — yield is from your balance.

Published practice page. Concentrations, masses, and numerical answers come from your school laboratory manual and your own readings — not invented here. Not yet reviewed by a named chemistry reviewer. Version 1.0.0, updated 2026-10-03.

Safety — read before you start

Safety warning. Practise here. Perform the real experiment only in your school lab, with your teacher present.

  • Oxalic acid toxic.
  • FeCl₃ corrosive.
  • Ethanol flammable if used for washing.

Wear: Lab coat, Splash goggles, Gloves, as your teacher directs.

Follow your teacher’s disposal instructions. Do not pour leftovers down a household drain.

Loads only after you tap. Use the lab hands to pick up and use equipment (pointer hidden in the scene). Falls back to a flat diagram if WebGL is unavailable.

Aim

To prepare potassium trioxalatoferrate(III) trihydrate crystals using the reagents and quantities specified in your laboratory manual.

Methods and quantities can differ between schools. Follow your teacher's instructions.

Apparatus and chemicals

Apparatus and chemicals
ItemNote
BeakersFor mixing and heating if required.
Glass rodStirring.
Funnel and filter paperHot filtration if manual uses it.
China dishCrystallisation.
BalanceWeigh product.
Ferric chloride (FeCl3·6H2O)Use the concentration, mass, and volume values printed in your school laboratory manual. This page does not invent a numerical result for you.
Oxalic acid (H2C2O4·2H2O)Use the concentration, mass, and volume values printed in your school laboratory manual. This page does not invent a numerical result for you.
Potassium oxalate (K2C2O4·H2O)Use the concentration, mass, and volume values printed in your school laboratory manual. This page does not invent a numerical result for you.
Distilled water (H2O)Solvent.
Ethanol (if manual) (C2H5OH)For washing crystals — flammable.
Volumetric flask with calibration mark and meniscus
Make up to the mark after the solid has dissolved. Read the meniscus at eye level so the curve sits on the line.

Theory and reaction

Open

Oxalate is a bidentate ligand forming a stable complex with Fe3+: [Fe(C2O4)3]3-.

Potassium ions provide charge balance in the crystal lattice as K3[Fe(C2O4)3]·3H2O.

The complex is green; oxalate also acts as reducing agent in other contexts — here it coordinates Fe3+.

Ferric ion with oxalate and potassium oxalate gives potassium trioxalatoferrate(III) hydrate.

Procedure

  1. Weigh reagents per manual. Dissolve oxalic acid and potassium oxalate in water as directed.
  2. Add ferric chloride solution slowly with stirring. Note green colour of complex.Safety: Oxalic acid is toxic; ferric chloride is corrosive.
  3. Heat or cool as manual specifies for crystallisation.
  4. Filter crystals, wash with ethanol or cold water if directed, dry and weigh.

Observation table

Enter the readings from your school lab in the practical file below. This page does not fill them in for you.

Type the readings in your practical file

Calculation

Theoretical yield from limiting reagent and formula mass K₃[Fe(C₂O₄)₃]·3H₂O. Percentage yield from your masses.

Result

Report mass of green crystals and percentage yield if required.

Precautions

  • Oxalic acid is poisonous — wash spills and never ingest.
  • Ethanol wash away from flames.
  • Avoid excessive heating that decomposes oxalate.

Viva questions

Answer one question at a time. The full answers stay closed until you open them.

Question 1 of 4

Oxalate ion in this preparation acts mainly as…

Answer choices

Pick an answer first.

Show all questions and answers

  1. Oxalate ion in this preparation acts mainly as…

    Answer: A bidentate ligand to Fe³⁺. Reason: Each oxalate can bind through two oxygen atoms.

  2. Oxidation state of iron in [Fe(C₂O₄)₃]³⁻ is…

    Answer: +3. Reason: Fe³⁺ is common for this complex in school prep.

  3. Coordination number of Fe in the complex is often…

    Answer: 6. Reason: Three bidentate oxalates give six donor atoms.

  4. Green colour indicates…

    Answer: A ferric oxalato complex (as prepared). Reason: The trioxalatoferrate(III) complex is characteristically green.

Common mistakes

  • Adding ferric chloride too fast causing local precipitation.
  • Confusing product with Mohr’s salt (different colour and formula).
  • Reporting yield without weighing dried crystals.

Frequently asked questions

Can I do this at home?
No. Use this page to practise the order of steps and viva. Do the real experiment only in your school laboratory, with your teacher present.

Your practical file

Name, school, and roll number are optional and are not sent anywhere.

The practical file opens on this device.

Review

Not yet reviewed by a named chemistry reviewer. Published for practice only — follow your teacher and laboratory manual for quantities and safety.

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