CBSE Chemistry Viva Questions Class 12 2025-26
Ananya Gupta6 Jan, 2026
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Chemistry Viva Questions Class 12 2025–26 play a crucial role in helping students prepare for the CBSE practical examination.
These viva questions are designed to test a student’s understanding of experiments, chemical reactions, laboratory procedures, and core concepts from the CBSE Class 12 Chemistry syllabus. Unlike written exams, a viva focuses on conceptual clarity and the ability to explain answers confidently and logically.
Preparing chemistry class 12 viva questions helps students revise important topics such as chemical equations, reagents used in experiments, observations, precautions, and sources of error. It strengthens theoretical knowledge and connects it with practical application, which is essential for scoring well in practical exams.
Viva Questions Class 12 Chemistry 2025-26
Viva Questions for Chemistry Practical Class 12 With Answers
Here are the Viva questions for Chemistry practical class 12 with answers, which are an important part of the practical exam preparation.Q1. What is an indicator?
Answer: An indicator is a chemical substance that changes color at the endpoint of a titration.Q2. Why must you not rinse a titration flask?
Answer: A titration flask must not be rinsed because rinsing leaves liquid sticking to the flask, which increases the pipetted volume taken in the titration flask.Q.3. Why must the burette and pipette be rinsed with the solution with which they are filled?
Answer: Burette and pipette are rinsed with the solution they are filled with to remove any water sticking to their sides, which could otherwise dilute the solution and affect its concentration.Q.4. What is titration?
Answer: Titration is the process of adding one solution from a burette to another in a conical flask to complete a chemical reaction.Q.5. What is the weight of a rider?
Answer: The weight of a rider is 10 mg.Q.6. Why is the front door of the balance closed at the time of weighing?
Answer: The front door is closed to prevent vibrations caused by the operator’s breath, which can lead to inaccurate results.Q.7. What is the basicity of H₂SO₄?
Answer: The basicity of H₂SO₄ is 2.Q.8. What is the equivalent mass of KMnO₄ when it acts as an oxidizing agent in an acidic medium?
Answer: KMnO₄ loses 5 electrons per molecule in an acidic medium, so its equivalent mass is one-fifth of its molecular mass.Q.9. What will be the normality of 0.10M KMnO₄?
Answer: It will be 0.1 x 5 = 0.5 N.Q.10. What is the maximum weight that can be weighed on a chemical balance?
Answer: The maximum weight that can be weighed is 100 grams.Q.11. What is the principle of volumetric analysis?
Answer: The principle involves determining the concentration of a solution by allowing a known volume to react quantitatively with another solution of known concentration.Q.12. What volume of 10M HCl must be diluted with water to get 1L of 1M HCl?
Answer: To prepare 1L of 1M HCl, 0.1L of 10M HCl must be diluted with water.Q.13. What is an endpoint?
Answer: The endpoint is the stage during titration when the chemical reaction is just complete.Q.14. What is a standard solution?
Answer: A standard solution is one whose concentration is known.Q.15. Why should the oxalic acid solution be heated to around 60-70°C before titrating it with KMnO₄ solution?
Answer: Heating speeds up the reaction by promoting the formation of Mn²⁺ ions, which autocatalyze the reaction. It also expels CO₂, allowing the reaction to proceed to completion.Q.16. What are primary and secondary standard substances?
Answer: A primary standard is a substance of high purity, stability, and solubility, while a secondary standard lacks these properties and is less stable.Q.17. Is sodium hydroxide a primary standard?
Answer: No, sodium hydroxide is not a primary standard. It is a secondary standard.Q.18. What is the difference between molality and molarity?
Answer: Molality measures the number of moles of solute per 1000 grams of solvent, whereas molarity measures the number of moles of solute per liter of solution.Q.19. What is a normal solution?
Answer: A normal solution contains one gram-equivalent mass of solute per liter of solution.Q. 20: Why should you not blow out the last drop from the pipette?
Answer: The last drop in the pipette represents extra liquid that is not included in the measured volume, so blowing it out leads to an inaccurate measurement.Q 21: What is acidimetry and alkalimetry?
Answer: Acidimetry and alkalimetry are methods of volumetric analysis that involve the chemical reaction between an acid and a base to determine their concentrations.Q 23: Why does KMnO₄ act as its own indicator in titrations?
Answer: KMnO₄ itself acts as an indicator because, when it is in excess, it imparts a pink color to the solution, signaling the endpoint of the titration.Q 24: Why are dilute H₂SO₄ and not other acids used in KMnO₄ titrations?
Answer: Dilute sulfuric acid is used in KMnO₄ titrations because it provides the necessary acidic medium for the reaction to occur without interfering with the reaction.Q 25: What is a standard solution?
Answer: A standard solution is a solution whose exact concentration is known, often used for titrations and determining the concentration of unknown solutions.Q 26: Why should a titration flask not be rinsed with water?
Answer: Rinsing the titration flask with water can introduce extra liquid that increases the volume in the flask, leading to an inaccurate measurement of the solution.Q 27: What is the principle behind volumetric analysis?
Answer: Volumetric analysis involves determining the concentration of a solution by reacting it with a solution of known concentration and measuring the volume required to complete the reaction.Q 28: Why are Mohr’s salt and not ferrous sulphate preferred in volumetric analysis?
Answer: Mohr’s salt is preferred over ferrous sulphate because it is more stable and does not get easily oxidized by air, unlike ferrous sulphate, which easily oxidizes to ferric sulphate.Q 29: Why should a burette with a rubber pinch cock not be used in KMnO₄ titrations?
Answer: A rubber pinch cock should not be used in KMnO₄ titrations because KMnO₄ can attack rubber, leading to contamination of the solution and inaccurate results.Q 30: What is the endpoint in KMnO₄ titrations?
Answer: The endpoint in KMnO₄ titrations is reached when the solution changes from colorless to a permanent light pink color, indicating the complete oxidation of the reducing agent.Marks Distribution for Chemistry Viva Questions Class 12 2025-26
The following is the marks distribution for CBSE chemistry class 12 viva questions, which includes different sections of the practical exam. Each section assesses specific skills and knowledge. Here's the detailed breakdown:| Topic | Marks Distribution |
|---|---|
| Experiment 1 (on Volumetric Analysis) | 8 marks |
| Experiment 2 (on Salt Analysis) | 8 marks |
| Experiment 3 (Based on Content) | 6 marks |
| Investigatory Project | 4 marks |
| Class Record and Viva-Voce | 4 marks |
| Total Marks | 30 marks |