Last Updated on October 18, 2026 by XAM CONTENT
This Class 12 Chemistry Practical and Viva Preparation Guide is built around the current CBSE 2026–27 Chemistry (Code 043) practical requirements. The practical examination carries 30 marks and evaluates quantitative analysis, salt analysis, a content-based experiment, project work, class record and viva. Use this guide to revise the chemical principle, observation, inference, calculation and reasoning behind the practical work already completed in your supervised school laboratory.
| Component | Marks |
|---|---|
| Volumetric Analysis | 8 |
| Salt Analysis | 8 |
| Content-Based Experiment | 6 |
| Project Work | 4 |
| Class Record and Viva | 4 |
| Total | 30 |
| Area | What You Should Understand |
|---|---|
| Surface Chemistry | Lyophilic/lyophobic sols, stability of colloidal systems and the observable behaviour of dispersions. |
| Chromatography | Separation of components, movement of spots, stationary/mobile phases and interpretation of Rf values. |
| Functional Groups | How characteristic observations are used to infer selected functional groups in an unknown sample. |
| Food Tests | How observations can indicate carbohydrates or proteins in the prescribed context. |
| Inorganic Preparation | Purpose of crystallisation/preparation work and how purity, crystal formation and observations are discussed. |
| Quantitative Analysis | Standard solution, titration logic, endpoint, concordant readings, mole relationships and molarity calculation. |
| Qualitative Salt Analysis | Observation → inference → confirmatory reasoning for one prescribed cation and one prescribed anion. |
CBSE currently includes quantitative analysis and qualitative salt analysis in the mandatory section. The syllabus specifies the substances/ions that schools may use. For exam preparation, concentrate on how evidence supports an inference and on the calculation structure used in the experiment you performed at school.
| Stage | How to Think |
|---|---|
| Observe | Record the visible or otherwise teacher-approved observation accurately without jumping immediately to a conclusion. |
| Infer | State which ion or group the observation suggests based on the prescribed analysis scheme. |
| Confirm | Use the confirmatory evidence obtained in the supervised school practical to support or reject the preliminary inference. |
| Report | Write the final ion identification clearly and separately from the raw observation. |
Example: A pigment spot travels 3.0 cm while the solvent front travels 6.0 cm. What is Rf?
Answer: Rf = 3.0/6.0 = 0.50.
| Weak Record Entry | Better Scientific Writing |
|---|---|
| “The test is positive.” | Record the actual observed change first, then write the inference separately. |
| “The salt is X because I know it.” | State the preliminary evidence and the confirmatory evidence that supports the identification. |
| “Endpoint reached.” | Record the teacher-approved endpoint observation and the corresponding reading systematically. |
| “Rf = 0.5.” | Show the two measured distances and the ratio used to obtain the value. |
| “Experiment successful.” | State the actual result or conclusion connected to the aim. |
1. What is a standard solution?
Answer: A solution whose concentration is accurately known.
2. What are concordant readings?
Answer: They are closely agreeing repeated measurements that indicate the result is reproducible within the precision of the experiment.
3. Why must a chemical equation used in a quantitative calculation be balanced?
Answer: The coefficients in a balanced equation provide the stoichiometric mole ratio connecting reactants and products.
4. What is the difference between an observation and an inference?
Answer: An observation is what is directly detected or measured; an inference is the chemical conclusion drawn from that evidence.
5. Why is a confirmatory test important in qualitative analysis?
Answer: A preliminary observation can sometimes be consistent with more than one possibility. Confirmatory evidence increases confidence that the identified ion is correct.
6. Why does Rf have no unit?
Answer: It is a ratio of two distances measured in the same unit, so the units cancel.
7. Why can two components travel different distances in chromatography?
Answer: They can have different relative attractions for the stationary and mobile phases, so they move at different rates.
8. Why should a final concentration include a unit?
Answer: Concentration is a physical quantity; its numerical value is incomplete without the concentration unit used.
9. What is the purpose of an investigatory project?
Answer: It gives the student an opportunity to investigate a focused question, organise observations or data, interpret results and communicate a reasoned conclusion.
10. What should you do if an experimental result differs from the expected value?
Answer: Do not alter the observation to fit the expected answer. Check calculations, units, instrument reading, procedure followed under supervision and possible experimental uncertainties, then report the result honestly.
How many marks are there for the Class 12 Chemistry practical?
The current CBSE Chemistry practical assessment carries 30 marks.
How are the 30 marks divided?
Volumetric Analysis 8, Salt Analysis 8, Content-Based Experiment 6, Project Work 4, and Class Record with Viva 4.
What is the best way to prepare for volumetric-analysis calculations?
Understand the balanced reaction, mole relationship, measured quantities and units. Practise the calculation structure using your teacher-approved school examples rather than memorising a final concentration.
How should I prepare salt analysis for viva?
Revise the observations recorded in your supervised school practical and practise explaining how each observation leads to a preliminary inference and how confirmatory evidence supports the final identification.
Should I memorise observation values or chemical-test results from another student’s file?
No. Your record should reflect the work completed in your own supervised school laboratory. For revision, understand the scientific meaning of your observations and calculations.
Where can I find the official practical list?
Use the current CBSE Class XII Chemistry 2026–27 curriculum linked at the top of this guide, together with the NCERT laboratory resources prescribed for the course.
