Most important Chemistry Practical viva-voce questions for titration: XII, XI Chemistry Practical Updated
Chemistry Practical viva-voce questions
Question 1. What is a standard solution?
Answer. A solution whose strength is known is called a standard solution.
Question 2: What is the molar mass of KMnO4?
Answer: 158g/mol
Question 3: What is the basicity of H2SO4?
Answer. 2.
Question 4. What is the weight of a rider?
Answer: 10 mg.
Question 5: What is the use of a rider?
Answer: A rider is used for weights less than 10 mg.
Question 6: 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 7: What is an indicator?
Answer: An indicator is a chemical substance that changes color at the end point.
Question 8: What is the end point?
Answer: When the reaction is just complete, it is known as the end point of titration.
Question 9: Why should a titration flask not be rinsed?
Answer. This is because during rinsing, some liquid will remain stuck to the titration flask; therefore, the pipetted volume taken in the titration flask will increase.
Question 10. Why must the burette and pipette be rinsed with the solution with which they are filled?
Answer: To remove any water sticking to their sides, which otherwise would decrease the concentration of the solutions to be taken in them.
Question 11: Why is it customary to read the lower meniscus in cases of colorless and transparent solutions and the upper meniscus in cases of highly colored solutions?
Answer: Because it is easy to read the lower meniscus in cases of colorless solutions and the upper meniscus in cases of colored solutions. In cases of colored solutions, the lower meniscus is not clearly visible.
Question 12. What is a molar solution?
Answer: A molar solution is a solution that contains one gm-mole of the substance in 1 L. This is symbolized as 1M.
Question 13: Why must the last drop of solution not be blown out of a pipette?
Answer. Because it is extra of the volume measured by the pipette.
Question 14: Which is an oxidizing agent and a reducing agent in the reaction between KMnO4 and Mohr’s salt?
Answer: KMnO4 acts as an oxidizing agent, and Mohr’s salt acts as a reducing agent.
Question 15. What is the indicator used in KMnO4 titration?
Answer: No indicator is used because KMnO4 acts as a self-indicator.
Question 16: Why does KMnO4 act as an indicator?
Answer: In the presence of dilute sulphuric acid, KMnO4 reacts with a reducing agent (oxalic acid or . Mohr’s salt). When all the reducing agent has been oxidized, the excess KMnO4 is not decomposed and imparts a pink color to the solution.
Question 17: What is the end point in KMnO4 titrations?
Answer: From colorless to permanent light pink.
Question 18: Why is Mohr’s salt preferred as a primary standard in volumetric analysis?
Answer: This is because Mohr’s salt is stable and is not readily oxidized by air.
Question 19: Why are a few drops of dilute sulfuric acid added while preparing a standard solution of Mohr’s salt?
Answer: A few drops of H2SO4 are added to prevent the hydrolysis of ferrous sulphate.
Question 20: Why should you heat the oxalic acid solution to about 60–70 °C before titrating with the KMnO4 solution?
Answer: In cold conditions, 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, and thus the reaction proceeds rapidly.
Question 21: What is the formula for Mohr’s salt?
Answer. The formula for Mohr’s salt is (NH4)2 . FeSO4 . 6H2O.
Question 22: What is meant by redox titration?
Answer: In redox titrations, both oxidation and reduction reactions take place simultaneously. During titration, one will get oxidized at the same time the other reactant will get oxidized while the other will get reduced, also called a redox reaction.
Ionic equations of titration of KMnO4 and Oxalic acid solution
Reduction Half reaction: MnO4– + 8H+ + 5e– → Mn2+ + 4H2O) x 2
Oxidation Half reaction: C2O42- → 2CO2 + 2e– ) X 5
Overall Ionic Reaction: 2MnO4– + 16H+ + 5C2O42- → 2Mn2+ + 10CO2 + 8H2O
Ionic equations of titration of KMnO4 and Mohr’s salt solution
Oxidation half reaction: [Fe2+ → Fe3+ – e–] x 5
Reduction half reaction: – MnO4– + 8H+ + 5e– → Mn2+ + 4H2O
Overall ionic equation: MnO4– + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O
Also Read : Mostly Asked Physics Practical Viva-Voce Questions
Questions on food tests
Question 1: What are carbohydrates?
Answer. Carbohydrates are polyhydroxy aldehydes, polydroxy ketones, or the compounds that yield these on hydrolysis. .
Question 2. Give two examples of monosaccharides.
Answer: glucose and fructose.
Question 3. Give two examples of disaccharides.
Answer: sucrose and maltose.
Question 4: What is Tollen’s reagent?
Answer: ammoniacal silver nitrate
Question 5: Why do we get a red ppt. in Fehling’s test?
Answer: Because of the formation of cuprous oxide (Cu20).
Question 6: Why do we get a shining mirror in Tollen’s test?
Answer: Due to the formation of silver, which deposits on the walls of the test tube.
Question 7: Name some reducing and non-reducing sugars.
Answer: Glucose and fructose are examples of reducing sugar, and sucrose is an example of non-reducing sugar.
Question 8: What are proteins?
Answer. Proteins are naturally occurring complex nitrogenous organic substances with high molecular masses. Chemically, they are polypeptides formed by the condensation of alpha-amino acids.
Question 9: How are proteins affected by heat?
Answer: They undergo coagulation.
Question 10: What is the biuret test for proteins?
Answer. To 2–3 ml of protein solution in a test tube, add NaOH solution. Mix thoroughly, and add a few drops of copper sulphate solution. A purple-violet color is obtained if protein is present.
Please note that these questions are not exhaustive, and you may need to refer to your course material for more information. Good luck with your practical!