Arsenic is a chemical element having the symbol As and the atomic number of arsenic is 33. It is a natural element that is found in rocks, soil, water, air, and plants and animals. It is a metalloid. Arsenic has many allotropes, but its gray form, which has a metallic appearance, important for industrial purposes.

Arsenic acid 

Arsenic acid is an arsenic oxoacid having one oxo group and three hydroxy groups attached with a central arsenic atom. It is conjugate acid of an arsenate (1-) and an arsenate ion. Arsenic acid, the liquid appears as a clear colorless aqueous solution and Noncombustible. Arsenic acid, solid appears as white crystals. It is also known as Orthoarsenic acid. It is used as wood preservatives, a finishing agent for glass and metal, and a reagent in the synthesis of some dyestuffs and organic arsenic compounds.

Formula of Arsenic acid  

The arsenic acid formula also known as Arsenic acid formula is presented in this article. Arsenic has 5 electrons, and it shares with 4 oxygen atoms. These 3 oxygen atoms complete their valance shell electron by sharing the electron with 3 hydrogen atoms. Which gives arsenic, 4 oxygen, and 3 hydrogen atoms. The atomic mass of arsenic acid is 141.94 g/mol. 

Structure of Arsenic acid

It is an arsenic oxoacid that consists of three hydroxy groups and one oxo group and these are attached to the central arsenic atom. Arsenic acid is a colorless solution. In its crystalline form, it is white and translucent. It is hygroscopic and non-combustible in nature.

 

Preparation of Arsenic acid

We can prepare the arsenic acid when we treating arsenic trioxide with concentrated nitric acid (HNO₃). As a byproduct, it produces dinitrogen trioxide.

As₂O₃ + 2HNO₃ + 2H₂O → 2H₃AsO₄ + N₂O₃

Then this solution is cool down to give a colorless crystal of the hemihydrate H₃AsO₄·1⁄2H₂O. and the dihydrate H₃AsO₄·2H₂O produces when the crystallization happened at lower temperatures.

Physical Properties of arsenic acid

1. It appears as a colorless aqueous solution.
2. Its solid appears as white crystals. 
3. It has a melting point of 35.5 °C.
4. It has a boiling point of 120 °C.
5. It is well soluble in water.

Chemical Properties of arsenic acid 

When we react arsenic with 3 molecules of H₂0 and ozone then it gives us arsenic acid. 

2As + 3H₂O + 5O₃ → 2H₃AsO₄ + 5O₂ 

Uses of Arsenic acid

1. It is used as a reagent in some dyes.
2. It is used as a finishing agent in metal and glass.
3. It is used sometimes in wood preservatives.
4. It is used as broad-spectrum biocide.

Sample Questions

Question 1: Is arsenic a slow poison?

Answer:

Arsenic, is consumed in large amounts and can kill a person rapidly. When we take it in a small amounts for a long period, it can cause serious illness or a prolonged death.

Question 2: What is arsenic acid used for?

Answer: 

Arsenic acid is used as a finishing agent in metal and glass. It is also used sometimes for wood preservatives, and it acts as a reagent in some dyes.

Question 3: Where is arsenic found?

Answer:

Inorganic arsenic compounds are found in soils, sediments, and groundwater. These compounds are found either naturally or in mining, ore smelting, and industrial use of arsenic.

Question 4: What is meant by arsenic acid?

Answer: 

It is a white poisonous soluble crystalline solid used in the manufacture of arsenates and insecticides, and the molecular and chemical formula of arsenic acid is H₃AsO₄. It is a colorless aqueous solution.

Question 5: What type of acid is arsenic acid?

Answer 

Arsenic acid is an arsenic oxoacid having one oxo group and three hydroxy groups attached to a central arsenic atom. It is non combustible in nature. 

Question 6: How strong is arsenic acid?

Answer: 

The arsenic carbon bonds are very stable but are split by heating with solid sodium hydroxide or chromium trioxide. This acid has a 6.2 pH value. Hence Arsenic acid is weak.