Question

The effect that trends to retard the mobilities of ions in solution is (a) asymmetry effect (b) relaxation effect (c) electrophoretic effect (d) all of these

Short answer

(d) all of these

Step-by-step solution

Understanding Ion Mobility

Ion mobility is the speed at which an ion moves in a field of force. Various factors can retard (i.e., slow down) this mobility, including the asymmetric nature of molecules, the relaxation effect, and the electrophoretic effect.

Analyzing the Effects

The asymmetry effect, the relaxation effect, and the electrophoretic effect, all are distinct phenomena that are known to retard ion mobility. The asymmetry effect retards ion mobility by disrupting uniform movement. The relaxation effect slows ion movement as it describes the time taken for ions to reach equilibrium in a solution after a force is applied. The electrophoretic effect refers to the motion of charged particles under influence of an electric field, which can also inhibit ion mobility due to interactions among charged particles.

Choosing the Answer

Given that all three effects can retard ion mobility, the correct answer is that all of these effects (asymmetry, relaxation, and electrophoretic) can retard the mobilities of ions in solution.

Key concepts

Asymmetry Effect

The asymmetry effect plays a critical role in slowing down the mobility of ions within a solution. When ions move through a solvent, they are typically surrounded by a symmetrical electric field. However, this symmetry can be disrupted by various factors, leading to what we call the 'asymmetry effect.'
This disruption occurs due to:

• The uneven distribution of surrounding molecules.
• Asymmetrical fields created as ions move.
• Influences from nearby particles or the shape of the ions themselves.

These factors create a varying pattern of forces that can cause ions to deviate from a straight path, reducing their speed. Understanding this concept helps to grasp why ions might not reach their destination as swiftly as expected in certain conditions.

Relaxation Effect

The relaxation effect is another phenomenon that affects ion mobility, occurring when ions take time to adjust to changes in their environment. When an external force, such as an electric field, is applied, ions don't immediately reach a state of equilibrium.
Let's break down the stages of this effect:

• Initial Disturbance: When the force is first applied, ions experience a disturbance.
• Adjustment Phase: It takes time for ions to rearrange themselves to settle into a new pattern or equilibrium.
• Equilibrium: Eventually, the ions stabilize, but this delay in adjustment results in a slower overall movement.

The 'relaxation' here refers to the time it takes for ions to settle after being disturbed, affecting how quickly they can move through a solution.

Electrophoretic Effect

The electrophoretic effect is a key consideration when examining ion movement in a solution. This effect describes the motion of charged particles within the solution under the influence of an electric field.
However, this movement is not purely straightforward due to several factors:

• The presence of other charged particles can lead to repulsive or attractive forces.
• These interactions cause drag forces that slow down ion mobility.
• The surrounding solvent also offers resistance, further retarding ion movement.

The collective impact of these interactions results in a less efficient movement of particles, highlighting the importance of considering the electrophoretic effect when studying ion dynamics in solutions.