Which Compound Has The Highest Melting Point?A. $Al _2\left( CO _3\right)_3$ B. $C _{12} H _{22} O _{11}$ C. $C _8 H _{18}$ D. $H _2 O$

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In chemistry, the melting point of a substance is a critical property that determines its physical state at a given temperature. It is the temperature at which a solid changes state to become a liquid at standard atmospheric pressure. The melting point of a compound is influenced by the strength of the intermolecular forces between its molecules. In this article, we will explore which compound among the given options has the highest melting point.

Understanding Intermolecular Forces

Intermolecular forces are the attractive and repulsive forces between molecules. These forces play a crucial role in determining the physical properties of a substance, including its melting point. The strength of intermolecular forces depends on the type of intermolecular force present in the substance. The three main types of intermolecular forces are:

  • London Dispersion Forces (LDFs): These are weak intermolecular forces that arise due to temporary dipoles in nonpolar molecules.
  • Dipole-Dipole Forces: These are stronger intermolecular forces that arise due to the interaction between permanent dipoles in polar molecules.
  • Hydrogen Bonding: These are the strongest intermolecular forces that arise due to the interaction between a hydrogen atom bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and another electronegative atom.

Analyzing the Given Compounds

Let's analyze the given compounds to determine which one has the highest melting point.

A. Al2(CO3)3Al _2\left( CO _3\right)_3

Aluminum carbonate (Al2(CO3)3Al _2\left( CO _3\right)_3) is a salt that consists of aluminum ions and carbonate ions. The carbonate ions are polar, and the aluminum ions are positively charged. This results in strong dipole-dipole forces between the ions, which contribute to the high melting point of aluminum carbonate.

B. C12H22O11C _{12} H _{22} O _{11}

Sucrose (C12H22O11C _{12} H _{22} O _{11}) is a sugar molecule that consists of carbon, hydrogen, and oxygen atoms. The molecule has a polar structure, with the oxygen atoms having a partial negative charge and the hydrogen atoms having a partial positive charge. This results in dipole-dipole forces between the molecules, which contribute to the melting point of sucrose.

C. C8H18C _8 H _{18}

Octane (C8H18C _8 H _{18}) is a nonpolar molecule that consists of carbon and hydrogen atoms. The molecule has a nonpolar structure, with no permanent dipoles. The only intermolecular forces present in octane are London dispersion forces, which are weak and do not contribute significantly to the melting point.

D. H2OH _2 O

Water (H2OH _2 O) is a polar molecule that consists of hydrogen and oxygen atoms. The oxygen atom has a partial negative charge, and the hydrogen atoms have a partial positive charge. This results in strong dipole-dipole forces between the molecules, which contribute to the high melting point of water.

Comparing the Melting Points

Based on the analysis above, we can conclude that the melting points of the given compounds are:

  • Al2(CO3)3Al _2\left( CO _3\right)_3: High melting point due to strong dipole-dipole forces
  • C12H22O11C _{12} H _{22} O _{11}: Moderate melting point due to dipole-dipole forces
  • C8H18C _8 H _{18}: Low melting point due to weak London dispersion forces
  • H2OH _2 O: High melting point due to strong dipole-dipole forces

Conclusion

In conclusion, the compound with the highest melting point among the given options is Al2(CO3)3Al _2\left( CO _3\right)_3. This is due to the strong dipole-dipole forces present between the ions in the compound. The other compounds have lower melting points due to weaker intermolecular forces.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
  • Chang, R. (2010). Chemistry: The central science (11th ed.). McGraw-Hill.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2007). General chemistry: Principles and modern applications (9th ed.). Pearson Prentice Hall.
    Frequently Asked Questions (FAQs) About Melting Points ===========================================================

In the previous article, we discussed the concept of melting points and analyzed the given compounds to determine which one has the highest melting point. In this article, we will answer some frequently asked questions (FAQs) about melting points.

Q: What is the melting point of a substance?

A: The melting point of a substance is the temperature at which it changes state from a solid to a liquid at standard atmospheric pressure.

Q: What factors affect the melting point of a substance?

A: The melting point of a substance is affected by the strength of the intermolecular forces between its molecules. The three main types of intermolecular forces are London dispersion forces, dipole-dipole forces, and hydrogen bonding.

Q: What is the difference between melting point and boiling point?

A: The melting point is the temperature at which a substance changes state from a solid to a liquid, while the boiling point is the temperature at which a substance changes state from a liquid to a gas.

Q: How do you measure the melting point of a substance?

A: The melting point of a substance is typically measured using a thermometer and a heating device, such as a Bunsen burner or a hot plate.

Q: What is the significance of melting point in chemistry?

A: The melting point of a substance is an important property in chemistry, as it can be used to identify and characterize a substance. It is also used in various industrial applications, such as in the production of pharmaceuticals and in the development of new materials.

Q: Can the melting point of a substance be changed?

A: Yes, the melting point of a substance can be changed by altering the intermolecular forces between its molecules. This can be done by adding impurities or by changing the temperature and pressure conditions.

Q: What are some common applications of melting points in chemistry?

A: Melting points are used in various applications in chemistry, including:

  • Identification of substances: Melting points can be used to identify and characterize a substance.
  • Purification of substances: Melting points can be used to purify a substance by separating it from impurities.
  • Development of new materials: Melting points can be used to develop new materials with specific properties.
  • Pharmaceutical applications: Melting points are used in the production of pharmaceuticals to ensure the purity and quality of the final product.

Q: What are some common mistakes to avoid when measuring melting points?

A: Some common mistakes to avoid when measuring melting points include:

  • Incorrect temperature measurement: Make sure to use a thermometer that is accurate and calibrated.
  • Inadequate heating: Make sure to heat the substance slowly and evenly to avoid overheating.
  • Insufficient data: Make sure to collect sufficient data to determine the melting point accurately.

Conclusion

In conclusion, melting points are an important property in chemistry that can be used to identify and characterize a substance. By understanding the factors that affect melting points and how to measure them accurately, chemists can use this property to develop new materials and improve existing ones.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
  • Chang, R. (2010). Chemistry: The central science (11th ed.). McGraw-Hill.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2007). General chemistry: Principles and modern applications (9th ed.). Pearson Prentice Hall.