Question

The interfacial forces are related to the contact angle by____.

• A. Nernest Equatio
• B. Stoke’s Equation
• C. Young’s Equation
• D. Laplace Equation

Answer 1

The Correct Option is C

The question asks about the relationship between interfacial forces and the contact angle. The correct answer is "Young’s Equation." Let's explore why this is the correct option and rule out the others.

Young's Equation: Young’s equation is a fundamental equation used to describe the contact angle formed by a liquid at a solid interface. It relates the contact angle, surface tension of the liquid in air, surface tension between the solid and air, and the surface tension between the solid and liquid. The equation is expressed as:

\(\gamma_{SG} = \gamma_{SL} + \gamma_{LG} \cos \theta\)

• \(\gamma_{SG}\): Surface tension of the solid-gas interface.
• \(\gamma_{SL}\): Surface tension of the solid-liquid interface.
• \(\gamma_{LG}\): Surface tension of the liquid-gas interface.
• \(\theta\): Contact angle.

This equation explains how the contact angle is formed based on the balance of these interfacial forces.

Other Options:

• Nernst Equation: This equation relates the reduction potential of a full electrochemical reaction to the standard electrode potential, temperature, activity, and reaction quotient. It is unrelated to interfacial forces and contact angles.
• Stoke’s Equation: This equation describes the force of viscosity on a sphere moving through a fluid. It is mainly used in fluid dynamics and does not concern interfacial forces or contact angles.
• Laplace Equation: This equation is significant in fluid dynamics but is mainly used to describe capillary action, bubbles, and droplets, studying pressures inside a fluid at rest or surface curvatures. It does not directly relate surface tensions to contact angles.

Hence, the correct relation between interfacial forces and contact angle is indeed given by Young’s Equation.