Volumetric Analysis Viva Questions with Answers

Chemical analysis is essential to study the components of a substance. Chemical analysis may be qualitative or quantitative. Volumetric analysis entails measuring the quantity of the reacting substances. The weight of a required component is indirectly obtained by measuring the amount of a solution containing an unknown amount of the required constituent that needs to react with a solution of known composition. This can be achieved with the help of titration.c

Table of Content

1. Aim

2. Apparatus Required

3. Theory

4. Procedure

5. Observation

6. Result

7. Precautions

Aim

To study the concept of volumetric analysis.y

Apparatus Required

• Graduated-burette

• Pipette

• Measuring flasks

• Measuring cylinders

• Titration flasks

• Beaker

• Tile

• Glass-rod

• Funnel

• Weighing bottle

• Wash bottle

• A chemical balance

Theory

A volumetric analysis measures the volumes of the solutions involved in the chemical reaction to determine the quantities of the constituents present in the given unknown solution. In this analysis, titration is the key process, which involves determining how much of a reagent is needed to complete a certain reaction. When strong acids are titrated with strong bases, they become chemically equivalent at the endpoint; this is known as a neutralization reaction. The pH of the solution suddenly changes near the endpoint. After the endpoint, even a small amount of base or acid would result in a mildly alkaline or acidic solution.

Procedure

• Burettes are thoroughly washed before filling with a solution to remove any greasy matter. 

• Ensure that a clean burette has no drops adhering to its inner wall. 

• Put a small amount of solution into the burette, close the top mouth with your thumb, and hold it in a horizontal position. Rotate the burette so that it wets every inch of the inside. Use the stop-cock to reject this solution. This process is called rinsing. 

• A funnel is inserted at the top of the burette to fill it. This solution is known as titrant. Once the burette has been filled, the funnel must be removed.

• After removing the parallax, the burette should be carefully read, because it forms the most important aspect of the experiment. 

• To read the burette, hold a sheet of a white paper called an anti-parallax card, behind the level of the liquid, so that it illuminates the surface of the liquid.

• Make an anti-parallax card by folding a rectangular piece of paper in half, making two cuts, opening the fold, and mounting it to the burette. Place your eye directly in front of the solution's meniscus and read the burette.

• A pipette is used to precisely measure the amount of a solution. It is a long tube with a jet at the lower end, and a cylindrical bulb in the middle.

• There is a circular mark on the upper part of the stem. Using the thumb and middle finger of the right hand, the upper end of the pipette is held, the lower end is dipped into the liquid, and the solution is drawn into the pipette until it reaches the mark about 2 cm above the liquid level. The solution is allowed to move gradually until the lower border of the meniscus touches the mark. Then it is released into the titration flask.

• Pipette out 10 ml of the solution into a conical flask that has been washed and dried, add 1-2 drops of indicator to the flask, and place it over the glazed tile. 

• The solution can be titrated with a titrant solution until a very faint color is obtained. 

• In the burette, read the lower meniscus again and record it as the final result. Repeat the procedure and take three concordant readings.

Volumetric analysis

Observations

The color change is observed and the burette readings are noted down.

To calculate the molarity of a solution, use the equation: a1M1V1 = a2M2V2 

Where M1 and V1 are the molarity and volume of the titrand. M2 and V2 are the molarity and volume of the titrant, and a1 and a2 are the basicity of the titrand and acidity of the titrant respectively.

Result

The concentration of the solution is ___ g/ml.

Precautions

• Ensure that no air bubbles are remaining in the narrow bottom tip of the burette. Using a stop-cock, the liquid is allowed to run rapidly out of the beaker or flask to remove the air. 

• The funnel should always be removed from the burette before noticing the readings and no drops should be hanging from the burette's nozzle.

• The level is read from the lower meniscus in the case of colorless solutions, and the upper meniscus in the case of colored solutions.

• Make sure the lower end of the pipette is always submerged in the liquid while sucking the liquid out, and don't pipette hot or corrosive solutions out.

Lab Manual Questions

1. What is the purpose of rinsing the burette and pipette with the solution that is being filled?

Ans: There will be very small amounts of liquid remaining after rinsing the burette and pipette with this solution. These tiny amounts will not affect the concentration of the solution. So it is necessary to rinse the burette and pipette with the respective solutions.

2. Why is the level read from the upper meniscus in the case of colored solutions?

Ans: The level is read from the upper meniscus in the case of colored solutions because colored solutions do not clearly show the lower meniscus.

3. What is an endpoint?

Ans: An endpoint is a point at which the amount of reactant necessary to complete a reaction has been added to a solution during the titration.

4. Why do you need to take a concordant reading?

Ans: Concordant readings are taken to ensure the accuracy of the final results of the titration since there are chances of errors during the titration.

Viva Questions

1. What are indicators?

Ans: Indicators are chemical compounds that change color when they are exposed to an acid or base.

2. What is the equivalent mass of crystalline oxalic acid?

Ans: The equivalent mass of crystalline oxalic acid is 63 g.

3. What is molarity?

Ans: Molarity is defined as the number of moles of a solute per liter of solution.

4. What is a 0.1M solution?

Ans: The solution which has one mole of solute per liter of solution is called 0.1M solution.

5. Define titration.

Ans: A typical laboratory technique for quantitative chemical analysis to ascertain the concentration of a specific analyte is titration.

6. What is molality?

Ans: The molality of a solution is the number of moles of solute per 1 kg or 1000 g of solvent.

7. Why do you use a funnel to fill the burette?

Ans: Funnel is used as a safety measure to prevent any liquid from the flask from spilling into the burette and interfering with the measurements.

8. What is a standard solution?

Ans: The solution of accurately known concentration is called a standard solution.

9. What is acidity?

Ans: The tendency of a compound to donate H+ is known as acidity.

10. How do you calculate molarity?

Ans: The molarity of a solution is calculated by the equation: a1M1V1 = a2M2V2.

Practical Based Questions

1. In an acid medium, how many moles of oxalic acid are oxidized by one mole of KMnO4?

A) 3

B) 4

C) 2.5

D) 2

Ans: C) 2.5

2. The amount of solute in gram-equivalents per liter of solution is called ___.

A) Molarity

B) Molality

C) Normality

D) Molecular mass

Ans: C) Normality

3. The point where the interaction between titrant and titrate is just about finished is called

A) Endpoint

B) Equivalence point

C) Titration point

D) None of the above

Ans: B) Equivalence point

4. What procedure is utilized to assess the strength of a specific solution?

A) Volumetric analysis

B) Chromatography

C) Calorimetry

D) Spectrophotometry

Ans: A) Volumetric analysis

5. The titration that includes both oxidation and reduction is called ___.

A) Acid-base titration

B) Redox titration

C) Complexometric titration

D) Precipitation titration

Ans: B) Redox titration

6. When titrating sodium carbonate against hydrochloric acid, which indicator is used?

A) Phenolphthalein

B) Starch

C) Methyl orange

D) Iodine

Ans: C) Methyl orange

7. The number of hydrogen atoms that can be replaced in an acid molecule is called

A) Basicity of a base

B) Basicity of an acid

C) Acidity of a base

D) Acidity of an acid

Ans: B) Basicity of an acid

8. Which of the following is an auto catalyst in a titration of oxalic acid vs. KMnO4?

A) Mn2+

B) O4

C) K+

D) Mn2-

Ans: A) Mn2+

9. Which color is produced by the phenolphthalein indicator in a basic medium?

A) Orange

B) Red

C) Pink

D) Blue

Ans: C) Pink

10.  What kind of reaction does acid-alkali titration involve?

A) Neutralization

B) Precipitation

C) Decomposition

D) Mineralization

Ans: A) Neutralization

Summary

Volumetric analysis entails measuring the quantity of the reacting substances. In this analysis, titration is the key process, which involves determining how much of a reagent is needed to complete a certain reaction. Pipette out 10 ml of the solution into a conical flask and add 1-2 drops of indicator. The solution can be titrated with a titrant solution until a very faint color is obtained. The color change is observed and the burette readings are noted down.