What is Sulfuric Acid?
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 337oC , and its melting point is 10oC.
Sulfuric acid uses
Some of the sulfuric acid uses are given below.
Fertilisers: Sulfuric acid is used in huge amounts to make phosphoric acid, which is used for the preparation of phosphate fertilisers.
Pharmaceuticals: It is used as a solvent for the chemical synthesis of a variety of chemical substances, including active pharmaceutical ingredients. One type of active pharmaceutical ingredient manufactured by using sulphuric acid are the alkylating agents which are commonly used in chemotherapy (treatment of cancer).
Gasoline: Sulfuric acid is also present in samples of gas for CEMS.
Automobile batteries: It is used in the manufacturing of Lead-Acid type batteries. In the automotive industry for cars and trucks, sealed-unit lead-acid type batteries are used.
Paper bleaching: In the pulp and paper industry, sulfuric acid is used for the on-site generation of chlorine dioxide, the key bleaching agent for the environmentally-friendly ECF chemical pulping process.
Water treatment: In wastewater treatment, an acid or a base is added, depending on the pH level of the water being treated. Either sulfuric acid or a base chemical is used to bring the pH level of wastewater back to normal, and this process is known as neutralisation.
Cellulose fibres: Sulfuric acid is also used for the making of cellulose fibres such as rayon fibre.
Steel manufacturing: Nowadays, petroleum refining is used effectively to wash impurities out of gasoline and other refinery products. It is used in processing metals, for example: in pickling or cleaning of iron and steel before plating with tin or zinc.
Colouring agents: It is used in the preparation of dyes, drugs, and disinfectants as colouring agents.
Regeneration of ion exchange resins: It is generally used to regenerate strong acid cation resins. It is used in order to control the precipitation of calcium sulfate. Regeneration with reduced concentrations of sulfuric acid at selected flow rates is necessary.
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:
Take a boiling tube and weigh 100mg of the sample in it.
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.
Na₂CO₃ is used to neutralise until the effervescence ceases.
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.
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.
Set a blank with 1mL of water.
1mL of phenol solution will be added to each tube.
5mL of 96% sulfuric acid will be added to each tube and shaken well.
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.
Read the colour at 490 nm.
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 applications. We get all the information, which is important such as sulfuric acid formula, its uses, electrolysis as well as manufacturing methods etc.
FAQs on Sulfuric Acid
1. What is sulfuric acid and what is its chemical formula?
Sulfuric acid is a highly corrosive and strong mineral acid with the chemical formula H₂SO₄. It is a dense, colourless, and oily liquid that is one of the most important industrial chemicals worldwide. Historically, it was known as 'Oil of Vitriol'.
2. Can you explain the molecular structure of sulfuric acid?
The structure of a sulfuric acid molecule (H₂SO₄) is tetrahedral. A central sulfur atom is bonded to two oxygen atoms with double bonds and to two hydroxyl groups (-OH) with single bonds. This arrangement is based on VSEPR theory to ensure maximum stability by minimising electron repulsion.
3. What are the main uses and applications of sulfuric acid in various industries?
Sulfuric acid is a vital component in many industrial processes. Its key applications include:
- Fertiliser Manufacturing: It is essential for producing phosphate fertilisers like ammonium sulfate.
- Chemical Synthesis: Used to manufacture a wide range of chemicals, including nitric acid, hydrochloric acid, dyes, pigments, and detergents.
- Metal Processing: Employed in the 'pickling' process to remove rust and other impurities from the surface of steel before it is plated.
- Automobile Batteries: Acts as the electrolyte in lead-acid batteries used in most vehicles.
- Petroleum Refining: Helps in washing impurities out of gasoline and other refinery products.
4. How is sulfuric acid manufactured on a large, commercial scale?
The primary method for commercial production of sulfuric acid is the Contact Process. This process involves three main steps: 1. Burning sulfur to create sulfur dioxide (SO₂). 2. Converting the sulfur dioxide into sulfur trioxide (SO₃) using a vanadium(V) oxide catalyst. 3. Absorbing the sulfur trioxide in concentrated sulfuric acid to form oleum (H₂S₂O₇), which is then diluted with water to yield sulfuric acid of the desired concentration.
5. What is the difference between concentrated and dilute sulfuric acid?
The main difference is the concentration of water. Concentrated sulfuric acid is nearly pure H₂SO₄ (around 98%) and is a powerful dehydrating and oxidising agent. Dilute sulfuric acid is a solution containing a much higher proportion of water. It behaves as a typical strong acid by readily ionising, making it a better electrolyte for applications like electrolysis.
6. Why is sulfuric acid often called the 'King of Chemicals'?
Sulfuric acid earns the title 'King of Chemicals' due to its extensive use across a vast number of industries and its massive global production volume. Its importance is so fundamental that a country's industrial development is often correlated with its sulfuric acid production levels. Its versatility makes it indispensable for manufacturing countless other products.
7. Why is it extremely dangerous to add water to concentrated sulfuric acid?
Adding water directly to concentrated sulfuric acid is extremely hazardous because the dissolution process is highly exothermic, meaning it releases a great deal of heat. Water is less dense than the acid, so it will float on top and the intense heat can cause it to boil instantly and violently, splashing the corrosive acid. The safe practice is to always add the acid slowly to a larger volume of water, allowing the water to absorb and dissipate the heat safely.
8. How does sulfuric acid act as a powerful dehydrating agent? Provide an example.
Sulfuric acid has a very strong affinity for water, allowing it to chemically remove water molecules from other substances. This makes it an excellent dehydrating agent. A classic example is its effect on sugar (sucrose, C₁₂H₂₂O₁₁). When concentrated H₂SO₄ is added to sugar, it strips away the hydrogen and oxygen atoms in a 2:1 ratio (as water), leaving behind a black, steaming column of pure carbon.
9. What are the key physical properties of sulfuric acid?
The important physical properties of sulfuric acid include its high density of approximately 1.83 g/cm³, a high boiling point of 337°C, and a melting point of 10°C. It is a viscous, oily liquid that is miscible with water in all proportions, though the mixing process releases a significant amount of heat.
