[Chemistry Class Notes] on Sulfuric Acid Pdf for Exam

Sulfuric acid (H₂SO₄) contains elements sulfur, oxygen, and hydrogen. It is known as oil of vitriol or hydrogen sulphate. It is one of the most important chemicals from the commercial point of view. The reaction of water and sulfur trioxide results as product sulfuric acid. The sulfur trioxide is made by the chemical combination of sulfur dioxide and oxygen or chamber process. In nature, pure sulfuric acid does not exist due to its strong affinity to water. It is supplied at different concentrations for different applications.        

                                    

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Sulfuric acid formula 

The sulfuric acid molecular formula is H₂SO₄. It has one atom of sulfur, four oxygen atoms attached to the sulfur atom and two hydrogen atoms attached with two oxygen atoms. Two oxygens are attached to the sulfur by a double bond, and two hydroxyl groups are attached by a single bond. It is an oxoacid of sulfur. According to the VSEPR Theory, The structure is arranged in such a way that there is minimum repulsion between lone pairs and bond pairs. Its molecular weight is 98.079 g/mol. Sulfuric acid density is 1.83g/cm³. Its boiling point is 337^oC , and its melting point is 10^oC.

Sulfuric acid uses

Some of the sulfuric acid uses are given below.

Electrolysis of concentrated sulfuric acid

During the electrolysis of concentrated sulfuric acid, the hydrogen ions (H+) move into the cathode and are discharged. Two reactions are given below that occur at the anode and cathode.

Anode: { 2H₂SO₄ → H₂S₂O₈ + 2H⁺ 2e^–

          2H₂O→ O₂ + 4H⁺ + 4e^–   }

Cathode: { 2H₂O → H₂ + 2OH^– – 2e^– } x 3

The final equation is as follows.

Equation: { 2H₂SO₄ + 8H₂O → H₂S₂O₈ + O₂ + 3H₂ +6H⁺ + 6OH^– }

Manufacture of sulfuric acid

For the production or manufacture of sulfuric acid, the material required is dry and clean sulfur dioxide gas. This is formed through the oxidation of elemental sulfur. Sulfur dioxide (SO2) in the presence of a vanadium catalyst is oxidised to sulfur trioxide (SO3) in the contact process at a high temperature. In concentrated sulfuric acid, sulfur trioxide is dissolved and forms oleum (fuming sulfuric acid).

From the sulfur element, it is manufactured in a three-stage process. These steps are as follows.

S + O₂ →  SO₂

2SO₂ +O₂ → 2SO₃

SO₃ + H₂O → H₂SO₄

Phenol sulfuric acid method

The phenol sulfuric acid method is one of the most reliable methods of carbohydrate analysis. The phenol-sulfuric acid method is used to find carbohydrates in a sample.  It is a simple and rapid colorimetric method. The concentrated sulfuric acid breaks down  In the phenol sulfuric acid method into any polysaccharides, oligosaccharides, and disaccharides into monosaccharides.

Material: Phenol 5%, sulphuric acid 96% reagent grade and Standard Glucose.

Process: 

1. Take a boiling tube and weigh 100mg of the sample in it.

2. Keep the boiling tube in water for around three hours with 5mL of 2.5 N-HCl in order to hydrolyse it, then cool it to room temperature.

3. Na₂CO₃ is used to neutralise until the effervescence ceases.

4. Now in the next step, make up the volume to 100mL and centrifuge into different test tubes, pipette out 0.2, 0.4, 0.6, 0.8 and 1mL of the working standard.

5. 0.1 and 0.2mL should be pipette out in two separate test tubes and make up the volume to 1mL with water in each tube.

6. Set a blank with 1mL of water.

7. 1mL of phenol solution will be added to each tube.

8. 5mL of 96% sulfuric acid will be added to each tube and shaken well.

9. After a duration of 10min, shake the content in the tubes and place in a water bath at a temperature between 25oC – 30°C for 20min.

10. Read the colour at 490 nm.

11. With the help of using the standard graph, calculate the amount of total carbohydrate present in the sample solution.

Do you know?

• One of the most important industrial chemicals in the world is Sulfuric Acid. It is also widely used in batteries of cars. The main producer of sulfuric acid is the United States of America and China.

• Oil of Vitriol is the name of sulfuric acid, which was used in history. In the medieval period, European Alchemists called it by this name because it was prepared in an iron retort by roasting “green vitriol”. 

Conclusion

Sulfuric acid is called the universal chemical and king of chemicals because it offers a wide range of applicatio
ns. We get all the information, which is important such as sulfuric acid formula, its uses, electrolysis as well as manufacturing methods etc.