Preparation of Solution of Oxalic Acid

What is oxalic acid? Oxalic acid is a chemical compound that has the chemical formula ${{C}_{2}}{{H}_{2}}{{O}_{4}}$ and bears the IUPAC name ethanedioic acid. It's considered the simplest dicarboxylic acid. A white crystalline solid forms a colourless solution once dissolved in water. The standard solution of ethanedioic acid is a known high-purity substance that may be dissolved to provide a primary standard solution in a known volume of solvent.

In the preparation of oxalic acid, several known solvent weights are dissolved. It's prepared using a standard, like a standard primary substance. Let us look into the preparation of ethanedioic acid solution.

Table of Content

• Aim

• Material Required

• Theory

• Procedure

• Result

• Observation

• Precautions

• Viva Questions

• Summary

Aim

To prepare 250 ml of M/10 solution of oxalic acid from crystalline oxalic acid.

Materials Required

• Weighing Tube

• Watch Glass

• Measuring Flask

• Beaker (250 ml)

• Glass Rod

• Chemical Balance

• Wash Bottle

• Funnel

• Funnel Stand

• Distilled Water

• Oxalic Acid

Theory

Many acids are obtainable in concentrated form, as they're required to be used in diluted type. Thus, they're mixed with water to acquire the required volume of diluted acid. Suppose the concentration of the concentrated acid is known. In that case, we can simply determine the volume of that individual acid that must be diluted to prepare a particular volume of dilute acid of the required concentration.

We can calculate the volume of the sample acid if the molarity of the targeted acid is known to us, the following molarity equation may be used to determine the molarity of the concentrated acid as described below:-

${{M}_{1}}{{V}_{1}}={{M}_{2}}{{V}_{2}}$

Where, 

M is the molarity of the concentrated acid 

V1 is the volume of concentrated acid,

M2 is the molarity of dilute acid,

V2 is the volume of dilute acid.

Suppose the normality of the targeted acid is known to us. In that case, the calculation for the amount of the acid needed is completed by the following formula:

${{N}_{1}}{{V}_{1}}={{N}_{2}}{{V}_{2}}$

Where,

The normality of concentrated acid is N1

V1 is the volume of concentrated acid

N2 is the normality of dilute acid,

V2 is the volume of dilute acid.

Formula for hydrated ethanedioic acid is ${{C}_{2}}{{H}_{4}}{{O}_{4}}.2{{H}_{2}}O$ .

2.6 g of ethanedioic acid/litre of the solution ought to be dissolved to produce an M/10 oxalic acid solution.

On the other hand, 12.6 /4 = 3.15 g of crystals of ethanedioic acid (oxalic acid) should be dissolved in water, and 250 millilitres of the solution should be precisely made.

Procedure

• Take a watch glass, wash it with Distilled water, and dry it properly.

• Weigh the precise amount of dried and clean watch glass and record its weight in the notebook.

• Weigh accurately on the watch glass 3.15 g of oxalic acid and note this weight inside the notebook.

• Transfer oxalic acid softly and thoroughly with the help of a funnel from the watch glass into a clean and dry measuring flask.

• Transfer gently and carefully the oxalic acid from the watch glass into a clean 250-milliliter beaker. 

• Wash the watch glass with distilled water using a wash bottle to transfer the particles sticking to it into the beaker.

• Dissolve oxalic acid crystals within the beaker by gently stirring with a clean glass rod.

• When the oxalic acid within the beaker is dissolved, carefully transfer the complete solution into a 250 ml measuring flask (volumetric flask) with a funnel

• Wash the beaker with distilled water. Transfer the solution mixture into the measuring flask.

• Finally, wash the funnel well with distilled water with the help of a wash bottle to transfer the solution left over to the funnel into the measuring flask.

• Add enough water to the measurement flask carefully, up to just below the etched mark thereon, with the help of a wash bottle.

• Add the last few drops of distilled water with a pipette till the lower level of the meniscus simply touches the mark on the measuring flask

• Stopper the measuring flask and shake gently to create the solution uniform throughout. 

• Label it as an oxalic acid solution. Now, calculate it as a solution of oxalic acid M/10.

Observations

Result 

250ml of (M/10) or 0.1 M solution of oxalic acid is prepared.

Precautions 

Following precautions ought to be taken while finishing the experiment:

• Wash the watch glass carefully, making sure that not even one crystal of oxalic acid is left on the watch glass.

• Using a pipette, add the remaining few drops to avoid an additional addition of distilled water to the mark above the neck of the measuring cylinder.

• If it's required to titrate oxalic acid or oxalate, add the required dilute amount of H2SO4 and heat the flask at a range of 60° - 70° C.

Lab Manual Questions

1. Why does oxalic acid solution boil before titration?

Ans. We heat the oxalic acid solution because without heat it's a slow method with much more energy than the activation power required to react. Thus to increase energy, the temperature ought to be increased which is only attainable by heating the oxalic acid solution.

2. What is the principle behind the estimation of oxalic acid?

Ans. Estimation is based on the reaction between KMnO4 and Oxalic acid. KMnO4 oxidizes oxalic acid in the presence of acid and while hot. Approximately 0.8g of oxalic acid is weighed, transferred into a 250 mL standard flask, and made up to the mark.

3. Does oxalic acid dissolve in hot water?

Ans. Oxalic acid crystals dissolve more readily in hot water than in a sugar solution. Tip: dissolve the oxalic crystals within the indicated amount of hot (150˚F) water before adding the sugar. Once the oxalic crystals are dissolved, only then stir in the sugar.

4. Is titration affected by temperature?

Ans. A temperature change will change the equilibrium constant, which can affect titrations in shifting equilibria in one direction or the other, adding sources of error in the titration process.

Viva Questions 

Q1.  Is oxalic acid a strong acid?

Ans. As an organic acid, oxalic acid could be a weak acid. Oxalic acid is understood to be a soft acid. It’s weaker than (water) H3O+ atoms. However, it's better than acetic acid, sulphuric acid, nitrous acid, carboxylic acid, etc.

Q2. Describe the procedure for the preparation of 1 normal oxalic acid.

Ans. If you dissolve ninety g of acid in 1 liter of water, it'll be 1 normal (N). To make 0.1 N, you wish to dissolve nine g of oxalic acid in one liter. If you wish to create one Molar acid, you ought to dissolve ninety g of acid in one kg of water.

Q3. How to prepare 250 ml of  M/20 solution of oxalic acid?

Ans. The molecular weight of oxalic acid is 126g.

Therefore, to prepare 250 ml M/20 oxalic acid solution:

(126×250)÷(20×1000) = 1.575 grams of oxalic acid is to be dissolved in water in a 250 ml volumetric flask.

Q4. Why is the standard solution always prepared in a volumetric flask?

Ans. A volumetric flask is employed when it's necessary to understand the volume of the solution prepared exactly and accurately. Volumetric flasks are calibrated (standardised) to specific volumes. This allows scientists to see how much liquid is contained in a specific flask once it's filled.

Q5. What is the standard solution?

Ans. A standard solution of known concentration is what the quality solution is called. Normal solutions are often created by dissolving a known quantity of the substance in a specific solvent volume.

Summary 

Oxalic acid, also called ethanedioic acid. It's a white crystalline solid that dissolves in water to generate a colourless solution. We can calculate the volume of the acid required to make a particular volume of the dilute solution if the molarity or normality of the concentrated acid is given and how 1M oxalic acid preparation is performed.

Practical Questions

1. Why does oxalic acid dissolve in water?

Ans. The slightly charged ends of water molecules attract these ions. As a result, the ions are dissociated or separated by the water molecules and spread equally throughout the solution.

2. What is the SI unit of normality?

Ans. Normality is represented by the letter “N.” The gram/liter is the SI unit. 

3. What is known as normality?

Ans. We define normality as the number of grams equivalent to solute present in a one-litre solution. So, the unit of normality is gram/litre. we tend to denote normality with the letter 'N'.

4. Where is normality used?

Ans. Normality is usually used in acid-base chemical reactions, oxidation-reduction reactions, and precipitation reactions. Thus it refers to the chemical process. Equivalent concentration refers to the solution's reactive capacity.

5. What is the endpoint in titration?

Ans. Endpoint: the point during a titration when an indicator shows that the amount of reactant necessary for a complete reaction has been added to a solution.