Which Compound Likely Has A Higher Melting Point: Aluminum Trichloride { (\text{AlCl}_3)$}$ Or Phosphorus Trichloride { (\text{PCl}_3)$}$?Use The Periodic Table To Support Your Claim.

Which Compound Likely Has a Higher Melting Point: Aluminum Trichloride or Phosphorus Trichloride?

In chemistry, the melting point of a compound is a critical property that can provide valuable information about its molecular structure and intermolecular forces. The melting point is the temperature at which a solid changes state to become a liquid. In this article, we will compare the melting points of two compounds: aluminum trichloride (AlCl3) and phosphorus trichloride (PCl3). We will use the periodic table to support our claim and explain why one compound likely has a higher melting point than the other.

The melting point of a compound is influenced by the strength of its intermolecular forces. Intermolecular forces are the attractive and repulsive forces between molecules. The stronger the intermolecular forces, the higher the melting point of a compound. There are several types of intermolecular forces, including:

• London dispersion forces: These are weak forces that arise from the temporary dipoles that form in nonpolar molecules.
• Dipole-dipole forces: These are forces that arise from the interaction between two polar molecules.
• Hydrogen bonding: This is a type of dipole-dipole force that occurs between molecules that have a hydrogen atom bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine.

Aluminum trichloride is a polar molecule with a trigonal planar geometry. The aluminum atom is bonded to three chlorine atoms, which are highly electronegative. This results in a significant dipole moment, which is a measure of the separation of charge within a molecule. The dipole moment of AlCl3 is 1.14 D, which is a relatively high value.

Phosphorus trichloride is also a polar molecule with a trigonal pyramidal geometry. The phosphorus atom is bonded to three chlorine atoms, which are highly electronegative. However, the phosphorus atom is also bonded to a lone pair of electrons, which results in a slightly lower dipole moment than AlCl3. The dipole moment of PCl3 is 0.96 D, which is a relatively low value.

The periodic table can provide valuable information about the properties of elements and their compounds. In this case, we can use the periodic table to compare the electronegativities of the elements involved in the two compounds.

Electronegativity is a measure of an atom's ability to attract electrons in a covalent bond. The higher the electronegativity of an atom, the more it will attract electrons and form a stronger bond. The periodic table shows that chlorine is a highly electronegative element, with an electronegativity value of 3.16. Aluminum, on the other hand, has a relatively low electronegativity value of 1.47.

Based on the information above, we can conclude that aluminum trichloride (AlCl3) likely has a higher melting point than phosphorus trichloride (PCl3). The stronger dipole moment of AlCl3 results in stronger intermolecular forces, which require more energy to overcome and result in a higher melting point. Additionally, the higher electronegativity of chlorine in AlCl3 results in a stronger bond between the aluminum and chlorine atoms, which also contributes to the higher melting point.

The melting points of AlCl3 and PCl3 are 192.4°C and -68.5°C, respectively. As expected, the melting point of AlCl3 is significantly higher than that of PCl3.

• CRC Handbook of Chemistry and Physics, 97th ed. (2016)
• NIST Chemistry WebBook, National Institute of Standards and Technology
• ChemGuide, Chemistry Guide (2019)

• Q: What is the melting point of aluminum trichloride? A: The melting point of aluminum trichloride is 192.4°C.
• Q: What is the melting point of phosphorus trichloride? A: The melting point of phosphorus trichloride is -68.5°C.
• Q: Why does aluminum trichloride have a higher melting point than phosphorus trichloride? A: Aluminum trichloride has a stronger dipole moment and stronger intermolecular forces, which result in a higher melting point.
  Frequently Asked Questions: Aluminum Trichloride and Phosphorus Trichloride ====================================================================

Q: What is the difference between aluminum trichloride and phosphorus trichloride?

A: Aluminum trichloride (AlCl3) and phosphorus trichloride (PCl3) are both polar molecules with a trigonal planar and trigonal pyramidal geometry, respectively. However, they differ in their electronegativity values and dipole moments, which affect their intermolecular forces and melting points.

Q: Why does aluminum trichloride have a higher melting point than phosphorus trichloride?

A: Aluminum trichloride has a stronger dipole moment and stronger intermolecular forces, which result in a higher melting point. The higher electronegativity of chlorine in AlCl3 results in a stronger bond between the aluminum and chlorine atoms, contributing to the higher melting point.

Q: What are the intermolecular forces present in aluminum trichloride and phosphorus trichloride?

A: Aluminum trichloride and phosphorus trichloride exhibit dipole-dipole forces, which are the primary intermolecular forces present in these compounds. The dipole-dipole forces in AlCl3 are stronger than those in PCl3 due to its higher dipole moment.

Q: How do the electronegativity values of aluminum and phosphorus affect the melting points of their respective trichlorides?

A: The electronegativity values of aluminum and phosphorus affect the melting points of their respective trichlorides by influencing the strength of the intermolecular forces. Aluminum has a lower electronegativity value than phosphorus, resulting in a stronger bond between the aluminum and chlorine atoms in AlCl3, which contributes to its higher melting point.

Q: What is the significance of the dipole moment in determining the melting point of a compound?

A: The dipole moment is a critical factor in determining the melting point of a compound. A higher dipole moment results in stronger intermolecular forces, which require more energy to overcome and result in a higher melting point.

Q: Can you provide examples of other compounds that exhibit similar intermolecular forces to aluminum trichloride and phosphorus trichloride?

A: Yes, other compounds that exhibit similar intermolecular forces to aluminum trichloride and phosphorus trichloride include:

• Sulfur trioxide (SO3): Like AlCl3, SO3 is a polar molecule with a trigonal planar geometry and exhibits strong dipole-dipole forces.
• Phosphorus pentachloride (PCl5): Like PCl3, PCl5 is a polar molecule with a trigonal bipyramidal geometry and exhibits weaker dipole-dipole forces.
• Boron trichloride (BCl3): Like AlCl3, BCl3 is a polar molecule with a trigonal planar geometry and exhibits strong dipole-dipole forces.

Q: How do the melting points of aluminum trichloride and phosphorus trichloride compare to other compounds in the same family?

A: The melting points of aluminum trichloride and phosphorus trichloride are relatively high compared to other compounds in the same family. For example, the melting point of aluminum chloride (AlCl) is 104°C, which is lower than that of AlCl3. Similarly, the melting point of phosphorus chloride (PCl) is -93°C, which is lower than that of PCl3.

Q: Can you provide a summary of the key points discussed in this article?

A: Yes, the key points discussed in this article are:

• Aluminum trichloride (AlCl3) has a higher melting point than phosphorus trichloride (PCl3) due to its stronger dipole moment and intermolecular forces.
• The electronegativity values of aluminum and phosphorus affect the melting points of their respective trichlorides by influencing the strength of the intermolecular forces.
• The dipole moment is a critical factor in determining the melting point of a compound.
• Other compounds that exhibit similar intermolecular forces to AlCl3 and PCl3 include sulfur trioxide (SO3), phosphorus pentachloride (PCl5), and boron trichloride (BCl3).