Content Curator
One phosphorus and three iodine atoms combine together to form phosphorus triiodide. It is an inorganic compound with the formula PI3 with a pyramidal molecular structure. There are two halides of phosphorus: Phosphorus trihalides where three is the covalency of phosphorous and Phosphorus pentahalide where the covalency of phosphorus is five. The hybridization of phosphorus and the electronic configuration affects phosphorus's chemical properties, which is why the uses of phosphorus triiodide differ from the other phosphorus trihalide.
| Table of Content |
Key Terms: Inorganic, Compound, Lone Pair, Phosphorus, Triiodide, Iodine, Water, Structure, Single Bond
Also Read: Phosphorus Trichloride
Phosphorus Triiodide
[Click Here for Sample Questions]
Phosphorus Triiodide is an inorganic compound with the formula PI3 with a pyramidal molecular structure. There are two halides of phosphorus - Phosphorus trihalides where three is the covalency of phosphorous and Phosphorus pentahalide where the covalency of phosphorus is five.
The hybridization of phosphorus and the electronic configuration affects phosphorus's chemical properties, which is why the uses of phosphorus triiodide differ from the other phosphorus trihalide.
Structure of Phosphorus Triiodide
[Click Here for Sample Questions]
The distorted tetrahedral structure of phosphorus triiodide is formed by three single bonds between iodine and phosphorus and a lone pair. The angle is less than tetrahedral because of the repulsion between the bond pair and the lone pair.
Preparation
[Click Here for Sample Questions]
The method in which the free elements combine together initiates the preparation of phosphorus trioxide. Iodine and the white phosphorus solution combine together in a neutral medium. The neutral medium is created when carbon disulfate is added to the preparation.
| P4 + 6l2 ð⇄ª 4PI3 |
Another method of preparing phosphorus triiodide is by converting other phosphorus halides such as phosphorus bromide and phosphorus chloride into phosphorus triiodide by adding metal iodide and hydrogen iodide which are iodine sources. Organic or inorganic sources of iodine can be used in this reaction.
| PCI3 + 3HI ð⇄ª PI3 + 3HCI |
Properties Of Phosphorus Triiodide
[Click Here for Sample Questions]
Physical and Chemical Properties of Phosphorus Triiodide are mentioned below:
Physical Properties Of Phosphorus Triiodide
Physical properties of phosphorus triiodide are as specified:
| Parameters | Details |
|---|---|
| State of matter | Solid form |
| Appearance | Dark red |
| Nature | Corrosive |
| Molecular weight | 411.6827g/mol |
| Density | 4.18g/cm3 |
| Boiling point | 200 degree Celsius |
| Melting point | 61.2 degree Celsius |
| Solubility | Soluble in water |
| Complexity | 8 |
| Heavy atom count | 4 |
| Covalently bonded unit | 1 |
| Odor | odorless |
Phosphorus Triiodide
Chemical Properties Of Phosphorus Triiodide
Chemical properties of phosphorus triiodide are as specified:
- Hydrogen iodide and phosphorus acid are formed when phosphorus triiodide reacts with water.
PI3 + 3H2O 🡪 H3PO3 + 3HI
- Trimethyl phosphine mercury is formed when methyl iodide and phosphorus triiodide are combined in the presence of mercury.
PI3 + 3CH3l + Hg 🡪 [(CH3)3 PHgl2 ]
- It consists of a weak P-I bond
- -46kg/mol is the standard enthalpy of formation of phosphorus trioxide
- Phosphorus triiodide acts as a good reducing agent
- Phosphorus triiodide is reactive in nature because of its unstable molecule.
- Phosphorus triiodide carries zero dipole movement.
Uses of phosphorus triiodide
[Click Here for Sample Questions]
- Phosphorus triiodide is well replaceable in the place of bromide in the manufacture of iodopyrazines.
- Used in the production of phosphoric acid by mixing it with water
- Aliphatic alcohols are converted into iodides by phosphorus triiodide which acts as a classic reagent.
- Used to convert alkane halide to alkane iodide.
- Hydroxyl groups are replaced by chlorine with the help of phosphorus triiodide which acts as a reagent.
Phosphorus Triiodide
Things to remember
- A large amount of heat is released when there is a reaction between phosphorus iodide and water.
- Phosphorus triiodide has the property to donate one lone pair of the electron to the electron deficit compound which is why it is known as an electrophile.
- It is highly toxic and corrosive in nature
- Phosphorus triiodide may affect one's health if not handled carefully
- The molecular shape of phosphorus triiodide is trigonal pyramidal
- Phosphorus triiodide is a red solid, inorganic compound that is commercially available and helps in converting alcohol to alkyl iodides.
Sample questions
Ques. What are the bond angles in the following molecular models: (4 Marks)
(1) PF3
(2) PCI3
(3) PBr3
(4) PI3
Ans. Molecular bonds for the followings are:
- 97 degrees
- 100 degrees
- 101.5 degrees
- 102 degrees
Ques. Why the bond angle of PI3 is more than that of PF3? (2 Marks)
Ans. With the increase in the density of phosphorus, the repulsion between the lone pair and the bond pair will be stronger. The increase in repulsion is directly proportional to the increase in the bond angle which is why the bond angle of PI3 is larger as compared to that of PF3.
Ques. What type of compound is phosphorus triiodide? (1 Mark)
Ans. Phosphorus triiodide is an inorganic compound that is formed by covalent bonding. Electrons are shared between the phosphorus atoms and three iodine atoms.
Ques. What are the different halides of phosphorus? (2 Marks)
Ans. PX3 and PX5 are the two kinds of halides of phosphorus. Phosphorus trichloride (PCI3) and phosphorus pentachloride (PCI5) are the two most common types of phosphorus halide.
Ques. What are the health issues caused by triiodide? (2 Marks)
Ans. it may cause irritation in the eyes, skin, and respiratory tract. It may also cause gastrointestinal irritation with vomiting, diarrhea, and nausea.
Ques. State five uses of phosphorus? (3 Marks)
Ans. Uses of phosphorus are specified below:
- helps in the formation of bones and teeth
- It helps the body to produce which is used in the maintenance, growth, and repair of the cells
- Uses in the manufacture of special glasses and fine chinaware
- Uses in the process of making steel
- phosphorus can be found in baking powder, fireworks, and fertilizers
Ques. What is the atomic number of phosphorus? (1 Mark)
Ans. The atomic number of phosphorus is 15. There are 15 atoms and 15 electrons in the atomic structure of phosphorus. It is a highly reactive element with the chemical symbol of P.
Ques. List out three health effects of phosphorus? (3 Marks)
Ans. The health effects of phosphorus are:
- Excessive use may cause osteoporosis and kidney damage.
- Excessive use of medicine can cause a deficiency in phosphorus.
- White phosphorus is the purest form of the element which can cause serious damage to our health and sometimes be fatal.
Ques. What is the appearance of triiodide? (2 Marks)
Ans. Triiodide appears Yellow in low concentrations and brown in higher concentrations. When iodine solution reacts with starch, it appears blue-black in color.
Ques. What are the properties of phosphorus? (3 Marks)
Ans. The physical properties of phosphorus are:
- There are four types of phosphorus: red, black, white, and purple
- Except for black phosphorus, all others are poor conductors of heat and electricity
- Phosphorous is stable at room temperature
Ques. What is the appearance of phosphorus? (1 Mark)
Ans. Phosphorus is colorless and semitransparent at room temperature. It is solid, soft, and waxy and glows in the dark.
Important PYQ’s Based On Phosphorus Triiodide
- The number of photoelectrons emitted for light… [NEET 2009]
- Which one of the following arrangements represents… [NEET 2005]
- Reaction between benzaldehyde and acetophenone… [NEET 2020]
Also Check:
| Chapter Related Topics | ||
|---|---|---|
| Oxoacids Of Phosphorus | Phosphorus Pentachloride | Modern Periodic Table |
| Atomic Mass Formula | Red Phosphorus | Phosphine |
Also Check:
| Chemistry Study Material | ||
|---|---|---|
| List Of Important Named Reactions In Organic Chemistry | Difference Between In Chemistry | Chemistry Formula |
Comments