Examples of London Dispersion Forces

📚 Quick Study Guide

• 🔬 London Dispersion Forces (LDF) are temporary attractive forces that occur when electrons are unevenly distributed around an atom or molecule, creating a temporary dipole.
• ⚛️ LDF exists between all molecules, whether polar or nonpolar. They are the ONLY intermolecular force present in nonpolar molecules.
• ⚖️ The strength of LDF increases with the size of the molecule (more electrons = stronger LDF).
• 🌡️ Boiling point and melting point increase with stronger LDF.
• $E_{potential} = - \frac{C}{r^6}$ where C is a constant and r is the distance between molecules

🧪 Practice Quiz

1. Which of the following molecules relies *solely* on London Dispersion Forces for intermolecular attraction?
   1. Methane ($CH_4$)
   2. Water ($H_2O$)
   3. Ammonia ($NH_3$)
   4. Ethanol ($C_2H_5OH$)
2. As the number of electrons in a molecule increases, the strength of London Dispersion Forces generally:
   1. Decreases
   2. Increases
   3. Remains constant
   4. Fluctuates randomly
3. Which of the following noble gases would you expect to have the *highest* boiling point?
   1. Helium (He)
   2. Neon (Ne)
   3. Argon (Ar)
   4. Krypton (Kr)
4. London Dispersion Forces are a result of:
   1. Permanent dipoles in a molecule
   2. Temporary dipoles caused by electron distribution
   3. Hydrogen bonding between molecules
   4. Ionic interactions between molecules
5. Which of the following hydrocarbons would exhibit the *strongest* London Dispersion Forces?
   1. $CH_4$ (Methane)
   2. $C_2H_6$ (Ethane)
   3. $C_3H_8$ (Propane)
   4. $C_4H_{10}$ (Butane)
6. The boiling point of a substance is *primarily* affected by the strength of its intermolecular forces. Which of the following would have the *lowest* boiling point?
   1. $I_2$ (Iodine)
   2. $Br_2$ (Bromine)
   3. $Cl_2$ (Chlorine)
   4. $F_2$ (Fluorine)
7. What type of molecules exhibit London Dispersion Forces?
   1. Only polar molecules
   2. Only nonpolar molecules
   3. All molecules (polar and nonpolar)
   4. Only ionic compounds