Question

Identify the three true statements. 1. Dipole-dipole interactions are stronger than dispersion forces and hydrogen bonds. 2. Hydrogen bonds require carbon, hydrogen, and a halogen. 3. Hydrocarbons exhibit only dispersion forces. 4. Boiling point generally increases with molecular weight due to increased strength of dispersion forces. 5. Stronger intermolecular forces usually correlate with higher boiling points.

Answer 1

Explanation:

Dipole-dipole interactions are defined as the interactions that occur when partial positive charge on an atom is attracted by partial negative charge on another atom.

For example, hydrocarbons show dispersion forces due to difference in the electronegativity of its combining atoms.

The weak intermolecular forces which can arise either between nucleus and electrons or between electron-electron are known as dispersion forces. These forces are also known as London dispersion forces.

Order of some forces in the order of increasing strength is as follows.

 Dispersion forces < dipole-induced dipole < dipole-dipole < hydrogen bonding < ion-dipole      

Boiling point is defined as the point at which vapor pressure of a substance becomes equal to the atmospheric pressure.

More is the mass or molecular weight of a substance more will be the bonding between its atoms. Hence, more heat is required to break these bonds.

As a result, higher will be its boiling point.

Therefore, out of the given options three true statements are as follows.

• Hydrocarbons exhibit only dispersion forces.

• Boiling point generally increases with molecular weight due to increased strength of dispersion forces.

• Stronger intermolecular forces usually correlate with higher boiling points.