Determination of Number of Molecules of Water of Crystallization with the Given 6.3g Oxalic Acid and 0.1M NaOH

Standard liquid solutions, like acids, are readily available and simple to prepare. The technique used in the quantitative analysis of any chemical is titration. A method for comprehending behaviour, known as quantitative analysis, makes use of statistical and mathematical modelling, observation, and investigation. Compounds called indicators are introduced to analyte solutions along with titrant.

Thus, this chemistry experiment explains determination of no. of molecules of water of crystallization with the given 6.3g oxalic acid and 0.1M NaOH. Oxalic acid is a dicarboxylic acid. It is indeed a white crystalline substance that dissolves in water to produce a colourless solution.

Table of Content

• Aim

• Apparatus Required

• Procedure

• Observations

• Result

• Precautions

Aim

To determine the value of no. of molecules of water of crystallization with the given 6.3g oxalic acid and 0.1M NaOH.

Apparatus Required

1. Burette stand

2. Burette

3. Conical flask

4. Measuring flask

5. Pipette

6. Glass rod

7. Funnel

8. Watch glass

9. Wash bottle

10.  Phenolphthalein

Theory

\[{\left( {COOH} \right)_2}.n{H_2}O + 2NaOH \to {(COONa)_2} + (n + {H_2}O)\] 

Indicator: Phenolphthalein

Endpoint: Colour shift to light pink colour.

Procedure

Determination of Value of No. of Molecules of Water of Crystallization with the Given 6.3g Oxalic Acid and 0.1M NaOH

1. Using distilled water, clean the burette.

2. Fill the burette using the provided 0.1M NaOH solution after rinsing it. 

3. Pipette 20 ml of the solution of oxalic acid prepared by the given 6.3g oxalic acid into a cleaned conical flask after rinsing the pipette with the provided oxalic acid solution. 

4. After adding 2-3 drops of phenolphthalein into the conical flask containing 20mL of oxalic acid, place it over the tile just below the tip of the burette.

5.  Record the burette's initial value and run the drops of NaOH solution to the conical flask gently until the permanent pale pink colour is obtained.

6. Keep track of the final measurement and calculate the volume of solution employed.

7. The procedure should be repeated to measure at a minimum of three concordant readings.

Observations

Calculation

Since there are 2 moles NaOH and 1 mole oxalic acid in the balanced equation

\[\dfrac{{{M_{NaOH}}{V_{NaOH}}}}{{{M_{oxalicacid}}{V_{oxalicacid}}}} = \dfrac{2}{1}\] 

\[\dfrac{{0.1 \times x}}{{{M_{oxalicacid}} \times 0.2}} = \dfrac{{0.1 \times x}}{{20.2 \times 2}} = \dfrac{x}{{400}}\]

\[{M_{oxalicacid}} = \dfrac{{Strengthperlitre}}{{Molarmassofoxalixacid}}\] 

\[Molarmassofoxalicacid = \dfrac{{Strengthperlitre}}{{{M_{oxalicacid}}}}\]

Molecular mass of oxalic acid= (90+18n) gmol-1

Equivalent weight of crystalline oxalic acid is 63 geq-1

Hence

\[ = \dfrac{{6.3}}{{\dfrac{x}{{400}}}} = 90 + 18n\] 

Calculating the value of n is possible once the titre value, x is known.

Result

The result of the chemistry experiment on the determination of no. of molecules of water of crystallization with the given 6.3g oxalic acid and 0.1M NaOH verified that:-

The number of molecules of water of crystallization in NaOH is (___).

Precautions

• Handle chemicals and apparatus with caution.

• Every apparatus should be rinsed with distilled water, and dried before starting the experiment.

• To prevent adding additional distilled water beyond the line on the measuring cylinder's neck, add the final few droplets employing a pipette.

• If any acid spills on your body, immediately wash it off with water. Apply a little ointment after that.

• After the completion of the experiment, wash your hands thoroughly.

Lab Manual Questions

1. What is the aim of transferring solutions using a glass rod?

Ans: Solutions are poured using glass rods to prevent spillage. A glass rod placed against a beaker's pouring edge enables the solution to run down the glass rod and into the collecting vessel, as opposed to splashing beyond the lip.

2. Why is it necessary to close the titration flask once the oxalic acid solution is prepared?

Ans: The solute's ability to interact with the moisture of the oxygen or absorb carbon dioxide or some additional pollutant in the air is dependent on the solute.

3. Why does not the pipette blow out the final drop?

Ans: Due to surface tension, a tiny drop of liquid remains in the pipette after the last drop is added, preventing the last drop from being blown out. Furthermore, the design of pipettes ensures that this drop won't have an impact on the empirical value.

4. What purpose does a burette serve?

Ans: A burette is a titration tool made of glass. It is utilised for regulating any volume of liquid within a specific range.

Viva Questions

1. Define molarity.

Ans: The number of moles of a solute per litre of a solution is known as molarity. Another term for molarity is the molar concentration of a solution.

2. What is the formula of hydrated oxalic acid?

Ans: The hydrated oxalic acid formula is (COOH)2.2H2O

3. What is the equivalent mass of oxalic acid?

Ans: Equivalent mass of oxalic acid (COOH)2 is 63 geq-1.

4. Find the value of x if the hydrated salt Na2CO3.xH2O is heated to become anhydrous by losing 63% loss of mass?

Ans: The value of x is 10.

5. What is the purpose of using the oxalic acid standard solution?

Ans: Oxalic acid standard solution can be employed to estimate an alkali solution's undetermined concentration.

6. Mention a few common indicators?

Ans: Methyl orange, phenolphthalein, starch, etc.

7. Why are burette and pipette rinsed using their solutions filled?

Ans: To get rid of anything that can stick to their edges and limit the amount of liquids they can hold, the burette & pipette are rinsed using the solutions they were loaded with.

8. Why should a pipette never be held by its bulb?

Ans: The glass bulb could expand due to body heat, which would cause a measuring inaccuracy.

9. What is the end point?

Ans: The end point of a titration is the point where the reaction is almost finished. Once a chemical process reaches its end point, it is considered to be complete. 

10. What does the term "concordant readings" refer to?

Ans: Volumetric analysis measurements that vary by less than 0.05 ml are considered concordant readings.

Practical-Based Questions

1. How many water molecules are associated with crystalline oxalic acid?

1. 2

2. 3

3. 4

4. 5

Ans: 2 water molecules are associated with crystalline oxalic acid.

2. What is the common name of solution in burette?

1. Analyte

2. Solvent

3. Titrant

4. None of the above

Ans: The solution used in the burette is the titrant.

3. Mention the indicator used in this chemistry experiment?

1. Phenolphthalein

2. Methyl orange

3. Starch

4. Methylene blue

Ans: The indicator used in this experiment is phenolphthalein

4. What is the common name of the solution in a conical flask?

1. Analyte

2. Solvent

3. Titrant

4. None of the above

Ans: The solution used in the conical flask is analyte.

5. What is the unit of molarity?

1. M or Moles L-1

2. N or eq L-1

3. Mol per kg

4. None of the above option

Ans: The unit of molarity is M or Moles L-1.

6. How many molecules of water of crystallization are present in citric acid?

1. 1

2. 2

3. 3

4. 4

Ans: 1 molecule of water of crystallization is present in citric acid.

7. Why rinsing a conical flask is not recommended?

1. Rinsing might cause the pipetted volume in conical flask to decrease

2. Rinsing might cause the pipetted volume in the conical flask to increase

3. Rinsing might cause the pipetted volume in the conical flask to precipitate

4. None of the three option

Ans: Rinsing might cause the pipetted volume in the conical flask to increase, hence it is not recommended.

8. What type of instrument is used in this experiment to add the last drop to avoid the extra drops in the solution while transferring solution in volumetric flask?

1. Dropper

2. Wash bottle

3. Pipette

4. None of the above three options.

Ans: Pipette is used to avoid extra drops during solution preparation

9. How is the strength of a particular solution determined?

1. Law of mass action

2. Equivalent law

3. Henry’s law

4. None of the three options

Ans: Equivalent law is used to determine the strength of a particular solution. 

10. How does distilled water act in chemical laboratories?

1. Indicator

2. Solvent 

3. Universal solvent

4. None of the three options

Ans: Distilled water acts as a universal solvent in chemical laboratories.

Conclusion

This chemistry experiment on the determination of no. of molecules of water of crystallization with the given 6.3g oxalic acid and 0.1M NaOH infers that the number of molecules of water of crystallization is determined using the titration of given 0.1M NaOH and prepared solution of given 6.3 g oxalic acid using phenolphthalein indicator. It is prepared utilizing only pure chemicals, and standardisation can be done to determine the precise concentration. An acid-base titration technique centered on the back titration employing a standard base after the sample has dissolved in excess of a standard acid.