What is the Function of Red Phosphorus in Reduction?
Phosphorous is an element that belongs to Group 15 and the 3rd period of the modern periodic table. The symbol was written as P It was first discovered by Hennig Brandt in the year 1669.There are many allotropes of Phosphorus which will be discussed later. The most common are white and red phosphorus.
The properties of phosphorus are given in the table below:
| Group | 15 | Atomic number | 15 |
| Period | 3 | Relative atomic mass | 30.974 |
| Block | p | State at 20°C | Solid |
| Melting point | 44.15°C, 111.47°F, 317.3 K | Key isotopes | 31P |
| Boiling point | 280.5°C, 536.9°F, 553.7 K | Electron configuration | [Ne] 3s23p3 |
| Density (g cm−3) | 1.823 | CAS number | 7723-14-0 |
However, phosphorus compounds mostly found their applications in fertilizers. For example, phosphate ores are used for making ammonium phosphate where firstly, the ores are being converted into phosphoric acids before the conversion of them to ammonium phosphate. Phosphates are also used in many detergents as one of the ingredients however, the use of it has begun to phase out in many countries. The main reason for this is that it causes a high level of phosphate content in most natural water supplies in places where the industries are set up as well as nearby places leading to the growth of unwanted algae affecting the ecology. For the production and making of fine chinaware and special glasses, phosphates are also important.
The allotropes of phosphorus are:
- White Phosphorus
- Red Phosphorus
- Black Phosphorous
- P2
The most commonly used or the main forms of P (phosphorus) are of two types. These include white phosphorus and red phosphorus. In a comparison of the two, Red phosphorous is a non-toxic solid whereas white phosphorous is a highly poisonous or toxic waxy solid which can cause acute burns when it comes in contact with the skin. The Red phosphorous is amorphous. The white P, in the absence of light, glows and when it is exposed to air, it is spontaneously and highly flammable. The main use of White phosphorus is in flares and devices that are probably designed to produce fire. Red phosphorus on the other hand is used mainly in matches where it consists of the material which gets stuck on the sides of a matchbox. This helps the matchsticks to light up when striking against it. Red phosphorus is believed to be more stable compared to white phosphorus and it has applications in many fields. The red phosphorus will be discussed
More in this article with its various applications.
What is Red Phosphorus?
One of the allotropes of the chemical element Phosphorus is known as red phosphorous. It is said to be derived from a P4 molecule.
Properties of Red Phosphorus
The various properties of this particular allotrope are given below:
- It is red in color.
- It is non-toxic in nature
- It isodorless
- It is less active and hence as a result it is more stable compared to white phosphorus. Red phosphorus does not have the phosphorescence property.
- Its molar mass is 30.974g/mol.
- It is an amorphous solid.
- Its melting point is 860K.
- Its density is 2.34g/cm3.
This allotrope of Phosphorous was discovered by Anton von Schrotter, an Austrian chemist back in the year 1845. He found out while the white phosphorous is being heated to 4820 F in a nitrogen environment for hours. This heating of white phosphorous leads to the formation of Red phosphorus.
Structure of Red Phosphorus
The Red phosphorus bears a polymeric structure where it consists of 4 Phosphorous atoms bonded together that are grouped tetrahedrally. In the red phosphorous, there is one broken P-P bond and there is a formation of another bond with the neighbouring tetrahedron that results in a chain-like structure.
How is Red Phosphorus being prepared?
As mentioned earlier, Red phosphorus is a result of the heating of white phosphorus. It is being prepared by heating white phosphorus up to about 4820F in a nitrogen atmosphere (inert environment) where iodine (I2) is used as a catalyst. The red phosphorous serves somewhatas an intermediary between the violet and the white phosphorus. Therefore, the allotropes of Phosphorous have a range of values that are related to their properties. Here is an example of such, ared phosphorous that is prepared freshly can ignite faster and is more reactive at 3000 ℃compared to a stored one which has a darker colour due to the prolonging storage period and becomes less reactive.
Applications of Red Phosphorus
This allotrope of P has a lot of applications. It is used in :
- The production of semiconductors.
- The production of fertilizers, pyrotechnics, and, pesticides.
Function in Reduction:
In reduction, the red phosphorus is used for the removal of Iodine present in HI. This forms PI3. The main reason for this is to prevent further reaction of iodine with alkane giving haloalkane. With this, we will not be able to get back the reduced compound if red phosphorus is absent as the iodination reaction is reversible.
Lear more concepts, refer: The P-block Elements from Class 12 Chemistry – Find All the Questions & Answers