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Most important viva-voce questions for titration - XII, XI Chemistry Practical

Updated: Apr 7, 2022

1. What is titration?

Ans. The process of adding one solution from the burette to another in the titration flask in order to complete the chemical reaction involved, is known as titration.


To calculate the strength (Molarity or Normality or amount of substance in g/l) of unknown solution with the help of unknown-solution with the by using burette, pipette, conical flask and indicators, is called titration.

2. What is indicator?

Ans. Indicator is a chemical substance which changes its colour at the end point.

3. What is end point?

Ans. The stage during titration at which the reaction is just completed is known as the end point of titration.

4. What is a normal solution?

Ans. A normal solution is a solution, a litre of which contains one gm-equivalent of the solute. This is symbolised as 1 N.

5. What do you mean by 1.0 M solution?

Ans. A solution containing 1 mole of solute per litre of solution is 1.0 M solution.

7. What is basicity of an acid?

Ans. It is the number of replaceable hydrogen atoms in a molecule of the acid.

8. What is acidity of a base?

Ans. It is the number of OH– ions furnished by a molecule of the base.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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 autocatalysis 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.

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