Chemistry Viva Questions

CHEMISTRY VIVA QUESTIONS 1.

What is volumetric or titrimetric analysis?

The analysis consisting of determining volume of a solution of accurately known concentration which is required to react quantitatively with the solution of the substances being determined is called volumetric or titrimetric analysis.

2.

What is standard solution ?

The solution of accurately known strength is called the standard solution and it contains known weight of the solute in a definite volume of the solution.

3.

What is meant by titration?

The process of adding a standard solution to a solute in solution until the reaction is just complete is termed as titration.

4.

Distinguish b/w titrant & titrate?

The reagent of known concentration is called the titrant & the substance being titrated is termed as titrate.

5.

Differentiate b/w equivalance & end point in titrations?

The point ay which the reaction b/w titrant & titrate is just complete is called equivalance point or theoretical point. The point at which a clear visual change is observed after the reaction b/w titrant & titrate is practically complete is called end point. Thus there exists a very small difference b/w the end point & equivalence point.

6.

How is the end point detected?

The completion of the titration (end point ) is detected by either a color change or the formation of turbidity in the liquid being titrated.

7.

What is an indicator?

A substance that facilitates the color change at the end point in titrations is called an indicator. E.g. methyl orange, phenolpthalein, starch.

8.

What is molar solution?

A solution which contains one gram molecular weight of the solute per dm3 of the solution is reffered as a molar solution. E.g. A solution containing 392 gram of FAS in 1 dm3 solution is called 1 molar solution.

9.

What is a normal solution?

A solution which contains one gram molecular weight of the solute per dm solution is called normal solution. 3

E.g. A solution containing 49 gram of K2Cr2o7 in 1 dm3 solution is called 1 normal solution.

10.what is molal solution? A solution which contains one gram molecular weight of the solution in one kilogram of the solution is called a molal solution. E.g. 58.45 gram of Nacl present in 1 kg of water is called 1 molal solution.

11.What is normality of solution? The normality of solution is the number of gram equivalents of the solute per dm of the solution. 3

Normality (N) of the solution = weight of solute/equivalent weight of solute

per dm

3.

12.what is molarity of a solution? The molarity of a solution is the number of gram equivalents of the solute per dm3 of the solution. molarity (M) of a solution = weight of solute/ molecular weight of solute per dm3 .

13 .what is meant by standardisation of a solution? Determination of the accurate strength of a solution using another standard solution by means of a titration is called standardisation of a solution.

14. what is meant by equivalent weight of an oxidising? parts 8

by

Equivalent weight of an oxidising agent is defined as the number of mass of the oxidising agent that gives parts by mass of oxygen for oxidation.

OR Equivalent weight of an oxidising agent =molecular weight/number of electrons gained. E.g. pottasium dichromate is an oxidising agent & in acid solution its reaction is represented as

Cr2o72- +14H- +6e-

----------> 2Cr3- + 7H20

Equivalent weight of K2Cr2O7= molecular weight / gained.

no. of electrons

= 294 / 6 = 49.

15. what is meant by equivalent weight of a reducing agent? Equivalent weight of a reducing agent is defined as the number of parts by mass of the reducsing agent that oxidised by 8 parts by mass of oxygen. OR Equivalent weight of a reducing agent =molecular weight / number of electrons lost. E.g. sodium oxalate acts as a reducing agent & is represented by

C2O42- ------> 2CO2 + 2e Equivalent weight of Na2C2O4 = molecular weight / number of electrons lost. = 134/2 = 67.

16. what is meant by equivalent weight of an acid? Equivalent weight of an acid is defined as the number of parts by mass of an acid that is neutralised completely by one equivalent weight of base.

OR Equivalent weight of an acid = molecular weight / basicity

E.g. Equivalent weight of H2SO4 = 98/2=49.

17.what is meant by equivalent weight of a base? Equivalent weight of a base is defined as the number of parts by mass of a base that is required to neutralise completely one equivalent weight of an acid. OR Equivalent weight of a base = molecular weight / acidity

E.g. Equivalent weight of NaOH =40/1=40

18. 0.6 g of K2Cr2O7 crystals are present in 250 cm 3 of the solution. calucate the normality of the solution. Equivalent weight of K2Cr2O7=49

(Equivalent in

normality of solution = - weght of K2Cr2O7 * 1000 cm3 / weight of K2Cr2O7* volume of solution cm3)

=(0.6 * 1000) = ( 49 *250 ) = 0.0489

19. what is molarity of solution containing 10g EDTA in 300 cm 3 of it ? Molarity of cm )/ ( molecular weight * 300 cm3 )

solution = (weight

of

solute *

1000

3

= (10 * 1000cm3)/(372.4 * 300 cm3) = 0.0895

20. How is 250 cm3 of 0.25N HCL prepared? given the normality of conc. HCl= 11.8 N1V1= N2V2 0.25* 250 = 11.8 *V2 V2 = 5.3 cm3 5.3 cm3 of the given conc. HCl on dilution upto 250 cm3 with water gives 0.25N HCl solutions.