Axit photphoric (H3PO4) là gì? Cấu tạo phân tử, tính chất, ứng dụng và phương pháp điều chế

Phosphoric acid (H3P04) is a toxic chemical but plays an important role in many manufacturing industries, especially fertilizer production and pesticides. What do you know about this chemical? Join Mầm non Cát Linh to find out important information about phosphoric acid in the following article!

View All

What is phosphoric acid definition?

Concept: Phosphoric acid is known for other names such as: trihidroxidixihotpho, phosphoric acid, orthophosphoric acid.

Chemical formula: H3PO4.

Molecular structure: Phosphoric acid has 3 hiccups. The molecular structure of this acid consists of 3 hydrogen molecules associated with PO4 root.

The physical properties of phosphoric acid

Phosphoric acid is a transparent crystal, exists in two forms: colorless crystal solids (infinite soluble in water or alcohol with uniform tetrahedron structure) and transparent liquid (colorless, sour). Typically, phosphoric acid is used in the form of a solid, comparable, colorless solution with a concentration of 85%.

• Water phosphoric acid is eager, easy to drain, soluble in water in any proportion.

• Melting temperature: 42.5 degrees Celsius

• Differentiate temperature: 213 degrees C.

• Density: 1.87 g/cm3

Chemical properties of phosphoric acid

Here are the typical chemical properties of phosphoric acid you need to remember.

Riddoing dissociators in 3 steps in the solution

Phosphoric acid is a 3 -step acid with average strength. In the water solution, H3PO4 will dissociate with 3 steps as follows:

• Hires 1: H3PO4 ↔ H + + H2PO4- (Mainly dissociation)

• Hires 2: H2PO4- ↔ H + + HPO4 (2-) (less dissociation)

• Hirp 3: HPO4 (2-) ↔ H + + PO4 (3-) (Very weak dissociation)

Thus, in the phosphoric acid solution there are H+, H2PO4-, HPO4 ions (2-), PO4 (3-) and H3PO4 molecules do not dissociate.

Phosphoric acid has the full properties of 1 acid

Phosphoric acid has the full chemical properties of an acid, including:

• Make purple kneeling red.

• Effect with basic oxide, creating products are salt and water:

2H3PO4 + 3NA2O → 2NA3PO4 + 3H2O

• Effects with bases to produce salt and water (different salt products depending on the reaction rate, such as acid salt, neutralized salt or mixture of those salt).

For example:

KOH + H3PO4 → KH2PO4 + H2O

2KOH + H3PO4 → K2HPO4 + 2H2O

3KOH + H3PO4 → K3PO4 + 3H2O

• Effect with metal before H2, create a product of salt and release H2:

For example: 2H3PO4 + 3mg → Mg3 (PO4) 2 + 3H2

• Effect with salt to create new salt + new acid:

For example: H3PO4 + 3AgNO3 → 3HNO3 + AG3PO4

• Pyrolysis reaction: At 200-250 ° C and 400-500 ° C, phosphoric acid shows oxidation-dehydration when a thermal reaction occurs.

2H3PO4 → H4P2O7 + H2O (temperature from 200 to 250 degrees C)

H4P2O7 → 2HPO3 + H2O (temperature from 400 to 500 degrees Celsius)

How to prepare phosphoric acid?

With important applications in manufacturing industries, what is the way phosphoric acid is created? Join Mầm non Cát Linh to learn how to prepare this acid in the laboratory and in industry.

Preparation of phosphoric acid in the laboratory

In the laboratory, phosphoric acid is prepared by using nitric acid HNO3 oxidized phosphorus at high temperatures:

P + 5HNO3 (concentrated) → H3PO4 + 5NO2 + H2O (Temperature)

Producing phosphoric acid in industry

In industry, phosphoric acid is produced by two methods: dry method and wet method.

• Wet method (extraction method)

This is how to use sulfuric acid that works with phosphoridite or apatite ore:

Ca3 (PO4) 2 + 3H2SO4 (concentrated) → 3CASO4 (precipitate) + 2H3PO4 (temperature)

After that, H3PO4 formed from the precipitate by filtering and concentrated. However, H3PO4 acid obtained by this method is not pure. To obtain pure acid with higher concentrations, people often use dry method.

• Dry method (heat process)

People burn phosphorus to create P2O5 phosphorus, then let P2O5 continue to react with water, the product obtained is pure H3PO4.

P → P2O5 → H3PO4

4p + 5O2 → 2p2O5 (temperature)

P2O5 + 3H2O → 2H3PO4

See also:

• Ammonium salt: Theoretical details and exercises with solutions
• Phosphate salt: Theoretical details and instructions for solving exercises

Outstanding applications of phosphoric acid

After grasping the structure, physical properties, chemicals and methods of preparing phosphoric acid, in this part, we learn the outstanding applications of H3PO4 in practice.

Application of phosphoric acid in agriculture

In agriculture, a large amount of phosphoric acid is used to produce fertilizers. H3PO4 concentrated can accommodate up to 70% -75% P2O5 – an extremely important ingredient in the preparation of phosphate salt, phosphate production, phosphorus compounds (in pesticides), animal feed …

Application of industrial phosphoric acid

Phosphoric acid has an important contribution in the industry with typical applications such as:

• Additive: Phosphoric acid is an additive in beverages, jams, jelly jelly, cheese … Besides, it can also create a fragrance, add sweetness, richness to the food by combining with HFCS (processed enzyme).

• Corrosion anti -corrosion: This is also a fireproof wood and metal corrosion resistant. Phosphoric acid is a raw material for producing glass tiles, water treatment, plating industry, producing detergents …

• Preservatives: H3PO4 has the ability to slow down the growth of bacteria and mold in sugar formulas should be used as preservatives.

• Producing dairy products: Phosphoric acid is also used to produce dairy products. The salt of this acid has the ability to change protein, pH to improve the quality of the product. Milk, butter and cheese … are typical examples of dairy products containing phosphoric acid.

• Pharmaceuticals: At the same time, H3PO4 is also used in pharmaceuticals.

The notes when using phosphoric acid

Phosphoric acid is quite important in industries and agriculture. However, we need to re -assert: Phosphoric acid is a toxic acid, causing many dangerous health consequences if used in the wrong way.

• Phosphoric acid is very volatile. Pay eyes, corneal burns, respiratory failure, fire, dangerous irritation … are dangerous symptoms when we are in direct contact with H3PO4 through the skin. Therefore, in the process of using phosphoric acid, you need to fully equip safe protection and knowledge about how to use this acid.

• H3PO4 is an ingredient in fresh water, it is also one of the risk factors that reduce bone density. Therefore, you should minimize the drink of bottled sweet drinks containing this acid.

• H3PO4 has the ability to react at high temperatures, which is easy to cause fire. Therefore, when using this acid, you need to close the average and store them in a dry place, avoiding the sun.

• In addition, H3PO4 is used in many different foods, the amount of phosphorus in these foods can make you increase the risk of kidney stones, urinary, … So read the ingredients in fast food and limit them. This is one of the potential risks that can be harmful to your health.

Exercise on chemical phosphoric acid 11 with detailed solutions

To master the knowledge of phosphoric acid, and Mầm non Cát Linh apply the theories learned above to practice some basic exercises about phosphoric acid in the following chemical textbooks.

Lesson 1 page 53 SGK Chemistry 11

Write the molecular chemical equation and the shortened ion form of the reaction between phosphoric acid with excess amount of:

a. Bag ; b. Ca (OH) 2; c. K2CO3

Solution:

The excess substances should be salted, neutralized salt:

a. 2H3PO4 + 3bao → Ba3 (PO4) 2 + 3H2O

The molecular equation coincides with the compact ion equation

b. 2H3PO4 + 3CA (OH) 2 → Ca3 (PO4) 2 + 6H2O

2H3PO4 + 3CA2 + + 6OH- → Ca3 (PO4) 2 + 6H2O

c. 2H3PO4 + 3K2CO3 → 2K3PO4 + 3H2O + 3CO2 ↑

2H3PO4 + 3CO32- → 2PO43- + 3H2O + CO2 ↑

Lesson 2 textbook chemistry 11 page 53

Indicate similarities and differences in chemical properties between nitric acid and phosphoric acid. Citing chemical reactions to illustrate?

Solution:

The common properties: are acidic

• Convert instruction color: Purple anemone turns red.

• Effects with bases, basic oxides with no reducing properties (elements with the highest oxidation number):

3naoh + H3PO4 → Na3PO4 + 3H2O

Fe2O3 + 6HNO3 → 2Fe (NO3) 3 + 3H2O

• Effect with some salts of weak acids and no reducing properties:

2HNO3 + CaCO3 → Ca (NO3) 2 + H2O + CO2 ↑

2H3PO4 + 3NA2SO3 → 2NA3PO4 + 3H2O + 3SO2 ↑

Different properties:

Lesson 3 textbook page 54 Chemistry 11

The total electrolytic equation of H3PO4 in the solution is:

H3PO4 ⇆ 3H + + PO43-

When adding HCl to the solution:

A. Balance on the shift in the direction.

B. The above balance shifts in the opposite direction.

C. The above balance is not moved.

D. PO43- concentration increases.

Solution: Answer B.

When adding HCl increases the concentration of H+ in the solution. According to the principle of balanced shift, balancing shift in the direction reduces H+ concentration

⇒ Balance shift in the opposite direction.

Lesson 4 page 54 chemistry 11 textbooks

a) Make the following chemical equations:

a. H3PO4 + K2HPO4 →

1 mol 1mol

b. H3PO4 + NaOH →

1 mol 1mol

c. H3PO4 + Ca (OH) 2 →

2mol 1mol

d. H3PO4 + Ca (OH) 2 →

2mol 3mol

Solution:

a. H3PO4 + K2HPO4 → 2KH2PO4

1 mol 1mol

b. H3PO4 + Ca (OH) 2 → CAHPO4 + 2H2O

1 mol 1mol

c. 2H3PO4 + Ca (OH) 2 → Ca (H2PO4) 2 + 2H2O

2mol 1mol

d. 2H3PO4 + 3CA (OH) 2 → Ca3 (PO4) 2 + 6H2O

2mol 3mol

Phosphoric acid is one of the important lessons in the high school chemistry program. Hopefully this article will help you master the most basic knowledge about H3PO4. Do not forget to apply it in chemistry practice exercises to master this lesson. Mầm non Cát Linh wishes you high results in learning!

References

Phosphoric Acid – Accessed date: July 23, 2022

https://en.wikipedia.org/wiki/phosphoric_acid

Phosphoric Acid – Accessed date: July 23, 2022

https://pubchem.ncbi.nlm.nih.gov/compound/phosphoric-acid

Nguồn: https://mncatlinhdd.edu.vn/ Tác giả: Nguyễn Lân dũng