The correct answer is A) Shows Tyndall effect.

Why Molecular Dispersion Does Not Show Tyndall Effect:

Molecular dispersion, also known as true solution, refers to a homogeneous mixture at the molecular level, where individual molecules of the solute are uniformly distributed throughout the solvent. In a molecular dispersion, the size of the solute particles is significantly smaller than the wavelength of visible light.

Due to this extremely small particle size, molecular dispersion does not exhibit the Tyndall effect.

The Tyndall effect is a phenomenon observed when light is scattered by particles or colloids suspended in a medium. The scattering of light occurs when the size of the particles is comparable to or larger than the wavelength of visible light, which causes the light to scatter in different directions, becoming visible to the naked eye.

This scattering effect is what gives colloidal suspensions their characteristic milky or hazy appearance.

In contrast, molecular dispersion lacks particles of sufficient size to scatter light significantly. Instead, it results in a clear, transparent solution where the solute molecules are evenly distributed and do not interfere with the passage of light.

Because the solute particles are at the molecular level and do not have a size comparable to the wavelength of visible light, there is no scattering of light, and hence, no Tyndall effect is observed.

Why the Other Options Are Not Correct:

B. Does Not Scatter Light (Correct for Molecular Dispersion):

This statement is correct for molecular dispersion. Molecular dispersion involves the dissolution of individual molecules in a solvent, leading to a solution that appears transparent and does not scatter light. The absence of light scattering is a defining characteristic of molecular dispersion.

C. Diffusion Rate is Rapid (May Vary):

The diffusion rate in molecular dispersion can vary depending on factors such as temperature, the nature of the solute and solvent, and concentration. While it is true that molecular dispersion often results in relatively rapid mixing and diffusion of solute molecules within the solvent, the actual diffusion rate can vary from one system to another.

D. Does Not Settle on Ultracentrifugation (May Vary):

Whether a molecular dispersion settles upon ultracentrifugation can depend on several factors, including the density of the solute and solvent, centrifuge conditions, and the presence of any stabilizing agents.

In some cases, molecular dispersions may remain stable and not settle upon ultracentrifugation, while in other cases, some settling or separation may occur. Therefore, the behavior of molecular dispersion upon ultracentrifugation can vary depending on the specific conditions and components involved.

In summary, molecular dispersion, characterized by the dissolution of solute molecules at the molecular level in a solvent, does not exhibit the Tyndall effect because its solute particles are much smaller than the wavelength of visible light.

The absence of light scattering is a distinguishing feature of molecular dispersion. While statements B, C, and D may be generally true under certain conditions, they are not inherent properties of molecular dispersion and can vary depending on the specific solute-solvent system and experimental parameters.