Titration Practical
This technique is used to determine the unknown concentration of an acid or a base by neutralizing it with an acid or base of known concentration. The process of determination of the strength of a solution of acid by titration with a standard solution of a base is termed acidimetry, on the other hand when the strength of a solution of an alkali is determined using titration with a standard solution of an acid it is called as alkalimetry. Now we will learn about the titration practical for titration of oxalic acid for the estimation of Sodium Hydroxide.
Aim
To determine the strength of the sodium hydroxide solution by titrating it against a standard solution of oxalic acid.
Theory
Here, the sodium hydroxide solution is not a primary standard and is taken in a burette and a known volume of the oxalic acid (a standard solution) is taken in the titration flask. The titration is carried out using phenolphthalein as an indicator. In an acid-base titration, the amount of acid becomes chemically equivalent to the amount of base present in the end. In the case of strong acid and strong base titration, the solution becomes neutral at the endpoint of the solution.
The reaction involved in the titration:
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Apparatus Required
Pipette
Burette
Burette stand
Conical flask
Stirrer
Measuring flask
Oxalic acid NaOH
Sodium hydroxide solution
Phenolphthalein indicator
Procedure:
Take a burette and wash it thoroughly with clean water and dry it.
Weigh the exact amount of dried watch glass and record its weight.
Using a funnel, shift oxalic acid carefully from the watch glass into a dried measuring flask.
Wash the watch glass with distilled water, the volume of distilled water should not be more than 50 ml.
Wash the funnel carefully using a wash bottle with distilled water, turn the flask of measurement until the oxalic acid dissolves.
Thoroughly add enough distilled water to the measuring flask just below the mark.
Add the last few drops of distilled water into the measuring flask until the reduced meniscus level just touches the mark.
Put the stopper on the mouth of the flask and shake it gently to make the entire solution uniform. Calculate the solution of oxalic acid M/20.
Estimation of Oxalic Acid by Titrating it with NaOH
Rinse the burette with the standard oxalic acid solution and take 10cm3 of oxalic acid solution in a titration flask. Fill the burette with sodium hydroxide solution and also remove the air gap if any.
In a pipette, take out 20ml of NaOH solution in a conical flask. Add two drops of phenolphthalein indicator into it and place it below the nozzle of the burette.
Now run the sodium hydroxide solution slowly and dropwise into the flask until a very faint permanent pink color is just obtained. Read the lower meniscus of the solution again in the burette and record it as the final burette reading. Repeat this procedure two to three times.
Observations
Molarity of oxalic acid solution = \[ \frac{M}{20}\]
Molarity of sodium hydroxide solution = m
The volume of oxalic acid solution = 10cm³
The indicator used = Phenolphthalein
Endpoint indication = Light pink colour
Calculations:
Mass of oxalic acid dissolved (100ml) in standard solution = x g
Estimation of sodium hydroxide
Strength of oxalic acid = X \[\times\] 10 g/L
Normality (N) of standard oxalic acid = Strength/ Equivalent weight = \[X \times \frac{10}{63.04}\]
Normality (N₁) of sodium hydroxide solution
\[N₁ x V₁ = N x V\]
\[N₁ = \frac{V}{V_1} \times N \]
Normality(N₂) of given oxalic acid solution
\[N₂ x V₂ = N₁ x V₁ \]
\[N_2 = \frac{V_1}{V_2} \times N_1 \]
Strength of given oxalic acid = N₂ x 63.04 g/L
Result: The strength of the given solution(NaOH) is _______ g/L.
Precautions
Wash the burette with water before and after titration is over.
Wash the watch glass carefully so that there is no crystal left on the watch glass.
The last few drops should be added using a pipette to avoid any extra addition of distilled water above the mark on the neck.
Properties of Sodium Hydroxide
Sodium Hydroxide is our main component in this titration process against oxalic acid. Let's understand some of the chemical properties of sodium hydroxide to understand the components used in the titration. Sodium hydroxide is an odorless and white crystalline substance that absorbs moisture from the air at the environmental or surrounding temperature. It's a synthetic chemical. When dissolved in water or neutralized with acid, it releases a significant amount of heat, which could ignite combustible objects. Sodium hydroxide is a highly corrosive substance. It's usually applied as a solid or a 50% solution. Caustic soda and lye are two more frequent names for this substance. Products like Dyestuffs, explosives, paper, rayon, Soaps, and petroleum are all made with the help of sodium hydroxide. Sodium hydroxide is also used in the processing of cotton and fabric, metal cleaning and processing, laundry and bleaching, electrolytic extraction, electroplating, and oxide coating, among other things. Commercial drain and oven cleansers frequently contain it.
Properties of Oxalic Acid
Another important component of titration is oxalic acid. Let's understand the properties of oxalic acid. The first member of the di-carboxylic acid group is oxalic acid. One molecule contains two carboxyl groups. Its potassium salt can be found in Rhubarb, Sorrel, and other oxalic group plants. Calcium oxalate is found in several plants and animals. It is created in the lab by oxidizing sugar cane sugar. It's created in a commercial setting by heating Sodium Formate. It comes in two forms: crystal and amorphous. Two molecules of Kelsan water make up one molecule of crystalline oxalic acid. The composition formula for amorphous oxalic acid is H2C2O4 and the molecular formula is H2C2O4.
Physical properties of Oxalic Acid
The physical properties of oxalic acid are also important to keep in mind from an exam point of view. The first thing to understand is that oxalic acid is present in a solid form that is colourless in its appearance and odourless in nature, that is there is no particular smell of it. Another form of oxalic acid is crystalline oxalic acid has a melting temperature of around 101.5°C, while anhydrous oxalic acid has a melting point of 189.5°C. Anhydrous oxalic acid is also soluble in alcohol and water and is unbreakable in ether.
FAQs on Titration of Oxalic Acid against Sodium Hydroxide
1. What is Titration Practical?
A caustic titration is a process where a solution of known concentration is used to determine the concentration of an unknown solution.
2. For the Titration Between Oxalic Acid and Sodium Hydroxide, Which Indicator is Used?
Phenolphthalein is chosen as an indicator because it changes colour in a pH range between 8 – 10. It appears pink in basic solutions and colourless in acidic solutions.
3. What is a Standard Solution and What is a Molar Solution?
A solution whose strength is known is termed a standard solution and the Molar solution is one that contains 1 mole of solute in one liter of solution.
4. Explain in brief the process of titration of oxalic acid?
The Titration process of oxalic acid can be understood in brief by the following process.
In a clean conical flask, take 10 ml of oxalic acid solution.
After this add 5ml of 1.0M sulphuric acid into it.
Before titrating the solution, heat it with the help of potassium permanganate solution in the temperature range of between 50-60℃.
At last to increase the visibility of the colour, keep the white tile below the conical flask.
5. Why is oxalic acid used as the primary standard?
One of the compounds in a titration must be used as a standard for which the amount of substance present is known precisely. This standard can be present in the form of a standard solution or a pure substance, a solution that is known for a precisely determined composition. There are only two ways to make a standard: employ the main standard or titrate against an already standardized solution. The number of moles present can be reliably estimated from the measured weight and the known molar mass of a primary standard, such as oxalic acid, which can be exactly weighed out in the pure form. For example, we could weigh out exactly 0.1 moles of primary standard oxalic acid and dilute it to one liter in a volumetric flask to make a 0.1000 molar solution.
In acid-base titration, the standard solutions do not always have to be primary standards. A secondary standard solution created by quantitative dilution of a primary standard is excellent. Titration against a primary standard solution can also be used to make secondary standards.
