Why PH3 has Lower Solubility than NH3?

What are PH3 and its properties? What are NH3 and its properties? Why is NH3 more Soluble than PH3? What could happen if PH3 and NH3 are placed in water? What Type of Reaction is between Water and NH3? 

Just as not every human is the same as another, similarly, every component or element is not the same. Though they may share some similarities, there are a few differences between them. Have you ever wondered why something is more soluble while the other is not like salt is more easily soluble than sugar? Since we are talking about solubility, can you tell me why PH3 has lower solubility than NH3? Why is NH3 more polar than PH3? What happens when PH3 is placed in water? Let’s begin and find the answers.

1. What is PH3?

It is a colorless, highly toxic, and flammable compound that has the chemical formula of PH3 and is known as phosphane or phosphine. It contains PH3 along with organophosphines that are derived from the process of substituting one or more hydrogen atoms with the organic group. Phosphine (PH3) is the smallest of the phosphates and phosphines. (See What is Boron Made of?)

2. What are the Chemical and Physical Properties of Phosphine?

This highly toxic gas has the following chemical and physical properties.

  • The smell of the phosphine is similar to that of a spoiled fish.
  • PH3 gives away its lone pair of electrons by reacting with hydrogen iodide which is why it acts as a Lewis base.
  • If it is exposed to the oxidizing agent, it will explode violently.
  • It is poisonous and dangerous with being sparingly soluble in water.
  • It can dissolve in natural solvents.
  • It is a colorless gas.
  • It is typically a non-ignitable gas.
  • It can burst into flames and turn into phosphoric acid if you warm it.
  • The melting point of Phosphine is -132.8° Celsius or -207.04° Fahrenheit or 140.35 Kelvin
  • It has a boiling point of -87.7° Celsius or -125.86° Fahrenheit or 185.45 Kelvin.

3. What is NH3?

Before moving ahead to know why PH3 has lower solubility than NH3, take a look at what is NH3. It is an inorganic compound of hydrogen and nitrogen that has the molecular formula of NH3. It is Ammonia, which is a colorless gas with a pungent smell that is distinct enough to be recognized. Ammonia is usually found in nature, and produced from vegetable matter and nitrogenous animals. (See What is Silicon Made of?)

4. What are the Chemical and Physical Properties of NH3?

Obtained from nature, this gas has the following properties:

  • It is a colorless gas.
  • It has a strong and pungent odor.
  • This gas is highly soluble in water.
  • When it reacts with acids, ammonium salts are formed.
  • It has a boiling point of −33.34° Celsius or −28.01° Fahrenheit or 239.81 Kelvin.
  • The melting point of ammonia is −77.73° Celsius or −107.91° Fahrenheit or 195.42 Kelvin.
  • In its pure form, it is known as anhydrous ammonia and readily absorbs moisture (hygroscopic).
  • It has alkaline properties that make it corrosive.
  • Not highly flammable but when exposed to high heat it may explode.
  • It is easily dissolvable in water forming a caustic solution and weak base.
  • Easily compressible.
  • It converts into a clear liquid under pressure.

5. What is Polarity?

You are close to finding out why PH3 has lower solubility than NH3. A molecule that is slightly positive at one end while slightly negative at another end is known as a polar molecule. The distribution of electric charge over the atoms that are joined by the bond is known as polarity. For example, in a water molecule, there are two components hydrogen and oxygen. Two charges are in the red and carry a negative charge while the other in blue carries a positive charge. (See What is the Empirical Formula of the Phosphorus Selenide?)

6. Why is NH3 More Polar than PH3?

The NH3 contains one atom of nitrogen and three atoms of hydrogen. However, the electronegativity of the nitrogen atoms is more in comparison to that of phosphorus. Even though the arrangements of atoms in both compounds are more or less the same, the difference in their electronegativity is the factor that decides their polarity. In this case, NH3 or Ammonia is more polar than PH3. So, why PH3 has lower solubility than NH3? Also, read Is NH3 polar or nonpolar?

7. Why PH3 has Lower Boiling Point than NH3?

Besides discussing why PH3 has lower solubility than NH3, note that PH3 or Phosphine molecules have less electronegativity that does not promote the formation of hydrogen bonding between the molecules. Whereas, Ammonia or NH3 have strong hydrogen bonding between the molecules. Since there is hydrogen bonding in NH3 and the same is lacking in PH3, therefore, NH3 has a higher boiling point than PH3. (See How does Calcium Chloride react with Chlorine?)

8. Why does PH3 not Form Hydrogen Bonds?

The reason why PH3 does not form hydrogen bonds lies in the atomic size and electronegativity of Phosphine molecules. Since Phosphine has a large atomic size but low electronegativity, it cannot form hydrogen bonds. However, NH3 or Ammonia has a small atomic size and its electronegativity is also high which enables it to form hydrogen bonds. (See Can Gasoline Evaporate?)

9. Why PH3 has Lower Solubility than NH3?

Ammonia or NH3 is polar and forms hydrogen bonds unlike PH3 or Phosphine, which cannot form hydrogen bonds and is not polar. So, why PH3 has lower solubility than NH3? The ability of Ammonia to form hydrogen bonds with water makes it more highly soluble in water than Phosphine (NH3). Since Phosphine cannot form hydrogen bonds with water, it has lower solubility. (See How many Oxygen Atoms are in SiO2?)

10. What Happens When PH3 is Placed in Water?

As the solution of PH3 comes in contact with water in the presence of light, it will give out red phosphorus and hydrogen. It means the molecules will break down giving out 1 molecule of phosphorus and 2 molecules of hydrogen. If you place PH3 in water bubbles will rise. (See What are the Components of Water?)

11. What happens when NH3 is Placed in Water?

If you place ammonia in water, you will notice that it is highly soluble and does not merely break down like PH3. Having high hydrogen bonding with water molecules, ammonia dissolves in water and forms a basic solution.

12. What Type of Reaction is between NH3 and Water?

The reaction in which ammonia molecules react with water is the hydrolysis reaction. It is the reaction in which one molecule breaks and forms multiple smaller molecules. In this reaction, NH3 or ammonia behaves like a Bronsted acid whereas water behaves like a Bronsted base. With ammonia dissolving in water forming a hydrogen bond with water due to its strong intermolecular forces, the reaction gets balanced. Check out what happens when water boils?

13. What are the Effects of PH3?

After learning about why PH3 has lower solubility than NH3, take a look at the effects of NH3. Since PH3 is a highly explosive gas if warmed under suitable conditions, it can cause huge damage. However, the effects experienced after a slight exposure are as follows:

  • Loose bowels
  • Cerebral pain
  • Dizziness
  • Cough
  • Chest tightness
  • If a person is exposed largely to this gas, the following symptoms are experienced.
  • Coma
  • Damage to the kidneys and liver
  • Convulsions
  • Irregular heartbeat

14. What are Uses of NH3?

Ammonia is obtained mostly from nature and is used widely in different industries. Here is a list of a few uses of ammonia:

  • An antimicrobial agent in food products
  • In fermentation industry
  • As fertilizers as it increases crop growth
  • As a pH adjuster in the fermentation process
  • As fuel for rocket engines
  • To neutralize pollutants like nitrogen oxides from diesel engines, etc.
  • As a household cleaner clean steel and glass
  • As a refrigerant
  • In the manufacturing of rayon and nylon
  • In the textile industries

So, today you learned about why PH3 has lower solubility than NH3. Who knows it could be because of the level of electronegativity of Phosphine. Along with why is NH3 more polar than PH3, did you notice what happens when PH3 is placed in water? Will it dissolve or break down? (See What is Sand Chemical Name?)

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