CBSE Class 12 Chemistry Viva Questions with Answers 2025, Download Practical Viva Solutions PDF

The CBSE assess the knowledge and preparation level of class 12 chemistry students by conducting the board exam. The CBSE Class 12 Chemistry board exam has two components: theory exam and practical exam. While most students prepare for theory examinations, they mostly overlook the practical viva voce. You can easily score good marks in the chemistry practical viva voce by going through the CBSE Class 12 Chemistry Viva Questions with Answers provided here.

CBSE Class 12 Chemistry Viva Questions

During the practical examination of class 12 chemistry in the CBSE board, an external teacher visit the school to examine students about their practical skills. The same external invigilator test the conceptual understanding of students by asking them oral questions. The CBSE Class 12 chemistry viva questions demand to the point answers.

The Class 12 Chemistry Practical Viva Voce Question and Answers aim to determine if the student has simply replicated the experiments from a textbook or if he/she has truly conducted them in the lab. Additionally, this aids in recalling the experiments conducted in the lab. Continue making revisions.

CBSE Class 12 Chemistry Viva Questions with Answers 2025

Class 12 chemistry viva voce questions and answers emphasize concepts rather than specific questions, enhancing the conceptual understanding linked to the practical activities conducted by the students. Students can review all chapter viva voce questions by looking at the provided question answers and build their confidence in them. A general viva voce relies on the practical concepts. Students can fully prepare for the CBSE Class 12 Chemistry Viva questions by going through the sample questions and answers provided here.

Viva Questions for Class 12 Chemistry Practical with Solutions

The overall marks for CBSE Class 12 Chemistry Practical amount to 30, split among various components such as experiments, project work, and practical files. Students need to obtain a minimum of 10 marks in the practical to pass the course. Students must be present for the practical exam on the scheduled date. It will take place solely in schools, and an outside examiner will oversee it. The most expected viva questions that the examiner will ask in the chemistry class 12 practical exam is given below with solutions:

Question 1. It is customary to read lower meniscus in case of colourless and transparent solutions and upper meniscus in case of highly coloured solutions, why ?
Answer: Because it is easy to read the lower meniscus in case of colourless solutions, while the upper meniscus in case of coloured solutions. In case of coloured solutions lower meniscus is not visible clearly.

Question 2. What is a molar solution ?
Answer: A molar solution is a solution, a litre of which contains one gm-mole of the substance. This is symbolised as 1M.

Question 3. Why the last drop of solution must not be blown out of a pipette?
Answer: Since the drops left in the jet end is extra of the volume measured by the pipette.

Question 4. Pipette should never be held from its bulb, why ?
Answer: The body temperature may expand the glass and introduce an error in the measurement volume.

Question 5. What is acidimetry and alkalimetry ?
Answer: It is the branch of volumetric analysis involving chemical reaction between an acid and a base.

Question 6. What is permanganometry ?
Answer: Redox titrations involving KMnO₄ as the oxidising agent are called permanganometric titrations.

Question 7. Which is an oxidising agent and a reducing agent in the reaction between KMnO₄ and FeSO₄?
Answer: KMnO₄ acts as oxidising agent and FeSO₄ acts as reducing agent.

Question 8. What is the indicator used in KMnO₄ titration ?
Answer: No indicator is used because KMnO₄ acts as a self-indicator.

Question 9. Why does KMnO₄ act itself as an indicator ?
Answer: In the presence of dilute sulphuric acid, KMnO₄ reacts with reducing agent (oxalic acid or . ferrous sulphate). When all the reducing agent has been oxidised, the excess of KMnO₄ is not decomposed and imparts pink colour to the solution.

Question 10. What is the end point in KMnO₄ titrations ?
Answer: From colourless to permanent light pink.

Question 11. Why is Mohr’s salt preferred as a primary standard over ferrous sulphate in volumetric analysis ?
Answer: This is because of the fact that Mohr’s salt is stable and is not readily oxidised by air. Ferrous sulphate gets oxidised to ferric sulphate.

Question 12. Why are a few drops of dilute sulphuric acid added while preparing a standard solution of Mohr’s salt ?
Answer: Few drops of H₂SO₄ are added to prevent the hydrolysis of ferrous sulphate.

Question 13. Why a burette with rubber pinch cock should not be used in KMnO₄ titrations ?
Answer: Because KMnO₄ attacks rubber.

Question 14. Sometimes a brown ppt. is observed in KMnO₄ titrations. Why ?
Answer: It is due to insufficient quantity of dil. sulphuric acid. Brown coloured ppt. (MnO₂.H₂0) is formed due to the incomplete oxidation of KMnO₄.

Question 15. Why should you heat the oxalic acid solution to about 60-70°C before titrating with KMnO₄ solution ?
Answer: In cold, the reaction is very slow due to the slow formation of Mn²⁺ ions. Oxalic acid is heated to speed up the liberation of Mn²⁺ ions which then auto catalyses the reaction and thus the reaction proceeds rapidly. This also serves the purpose of expelling the carbon dioxide evolved during the reaction which otherwise does not allow the reaction to go to completion.

Question 16. What is titration ?
Answer: The process of adding one solution from the burette to another in the conical flask in order to complete the chemical reaction involved, is known as titration.

Question 17. What is indicator ?
Answer: Indicator is a chemical substance which changes colour at the end point.

Question 18. What is end point ?
Answer: The stage during titration at which the reaction is just complete is known as the end point of titration.

Question 19. Why a titration flask should not be rinsed ?
Answer: This is because during rinsing-some liquid will remain sticking to the titration flask therefore the pipetted volume taken in the titration flask will increase.

Question 20. What are primary and secondary standard substances?
Answer: A substance is known as primary standard if it is available in high degree of purity, if it is stable and unaffected by air, if it does not gain or lose moisture in air, if it is readily soluble and its solution in water remains as such for long time. On the other hand, a substance which does not possess the above characteristics is called a secondary standard substance. Primary standards are crystalline oxalic add, anhydrous Na₂CO₃ , Mohr’s salt, etc.

Question 21. Burette and pipette must be rinsed with the solution with which they are filled, why ?
Answer: The burette and pipette are rinsed with the solution with which they are filled in order to remove any water sticking to their sides, which otherwise would decrease the cone, of the solutions to be taken in them.

Question 22. Why front door of the balance is closed during weighing ?
Answer: Opening the front door causes vibrations in the pan due to operator’s breath which leads to inaccurate results.

Question 23. What is the maximum weight that can be weighed in a chemical balance ?
Answer: 100 grams.

Question 24. What is the weight of a rider ?
Answer: 10 mg.

Question 25. What is the use of a rider ?
Answer: A rider is used for weights less than 10 mg.

Question 26. What is the principle of volumetric analysis?
Answer: In volumetric analysis, the concentration of a solution is determined by allowing a known volume of the solution to react, quantitatively with another solution of known concentration.

Question 27. What volume of 10M HCl must be diluted with water to get 1L of 1M HCl ?
Answer: 0.1L.

Question 28. What is the basicity of H₂SO₄ ?
Answer: 2.

Question 29. What is the relationship between normality (N), molarity (M), molecular mass and equivalent mass ?
Answer: Normality x Eq. Mass = Molarity x Mol. Mass.

Question 30. Is sodium hydroxide a primary standard ?
Answer: No.

Question 31. Are ‘molality’ and “molarity’’ same ?
Answer: No, molality of a solution is defined as the number of moles of solute present in 1000 grams of the solution whereas molarity tells us about the number of moles of the solute present per litre of the solution.

Question 32. What would be the normality of 0.10M KMnO₄ ?
Answer: It will be 0.1 x 5 = 0.5 N.

Question 33. What is a standard solution ?
Answer: A solution whose strength is known is called a standard solution.

Question 34. What is a normal solution ?
Answer: A solution containing one gram-equivalent mass of the solute per litre of the solution is called a normal solution.

Question 35. What is the equivalent mass of KMnO₄ when it acts as oxidizing agent in acidic medium ?
Answer: KMnO₄ loses 5 electrons per molecule, when it acts as oxidizing agent in the presence of acids. Therefore, its equivalent mass is one-fifth of its molecular mass.

Viva Questions for Chemistry Practical Class 12 with Answers PDF Download

The Viva Voce in the Class 12 Chemistry practical assessment serves not only as an evaluation but also as a chance to showcase conceptual understanding and enhance confidence. Revising the sample questions with answers will enable you to approach the Viva with ease and confidence. Download the free PDF with CBSE Class 12 Chemistry viva questions with answers for free from below.

CBSE Class 12 Chemistry Viva Questions with Answers

Sharing is caring!