Question

The ionic mobility of alkali metal ions in aqueous solution is maximum for: (a) \(\mathrm{K}^{+}\) (b) \(\mathrm{Rb}^{+}\) (c) \(\mathrm{Li}^{+}\) (d) \(\mathrm{Na}^{+}\)

Short answer

The ionic mobility is maximum for \( \mathrm{Rb}^{+} \).

Step-by-step solution

Understand Ionic Mobility

Ionic mobility refers to the speed at which an ion moves through a solvent under the influence of an electric field. It is influenced by factors such as ion size and solvation.

Analyze Ion Size and Solvation

Larger ions tend to have lower solvation because they can carry a smaller number of water molecules per volume. Hence, larger ions have greater ionic mobility as they experience less drag from solvated water molecules.

Compare Sizes of Alkali Metal Ions

Based on atomic sizes, the order from smallest to largest alkali metal ions is: \( \mathrm{Li}^{+} \), \( \mathrm{Na}^{+} \), \( \mathrm{K}^{+} \), \( \mathrm{Rb}^{+} \). Since solvation decreases with ion size, \( \mathrm{Rb}^{+} \) will have the least solvation.

Conclude the Maximum Ionic Mobility

Since \( \mathrm{Rb}^{+} \) is the largest ion among the given options, it has the least solvation and therefore the maximum ionic mobility in aqueous solution.

Key concepts

Alkali Metals

Alkali metals are a fascinating group in the periodic table, known for their highly reactive properties and occurrence in Group 1. These elements include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), among others. These metals are characterized by their single electron in the outermost shell, which makes them eager to participate in chemical reactions.

In solutions, alkali metals form positive ions by losing this single electron. Their reactivity doesn’t just stop there. As move down the group from Li to Rb, their atomic size increases, which affects various properties, including ionic mobility.

These metal ions easily dissolve in water, leading to interesting behaviors under chemical and physical influences, such as electric fields. The dynamics of how they move in solutions is an essential aspect of chemistry, particularly in understanding conductivity and reaction rates.

Ion Solvation

Ion solvation is the process by which water molecules surround and interact with ions in a solution. When alkali metal ions are dissolved in water, they attract water molecules due to electrostatic forces. This attraction results in a solvation shell, a cluster of water molecules surrounding the ion.

The extent of solvation depends largely on the size and charge of the ion. Smaller ions tend to have stronger solvation because they can strongly attract water molecules, whereas larger ions experience weaker solvation.

• Solvation influences ion mobility; smaller, heavily solvated ions tend to move slower.
• Larger ions, by contrast, experience less solvation drag and therefore move more freely.

Understanding solvation is crucial when studying solution chemistry, as it affects everything from reaction rates to the biological uptake of nutrients.

Aqueous Solutions

An aqueous solution is simply any solution in which water is the solvent. Water's polar nature makes it an excellent solvent, allowing it to dissolve ionic and molecular compounds effectively. In the context of alkali metals, when these metals dissolve in water, they form ions that can move freely in the solution.

Aqueous solutions are vital in various scientific and industrial applications due to their ability to conduct electricity, which is immensely useful in electrochemistry. The ionic compounds in these solutions dissociate into their respective ions, allowing them to conduct an electric current when an electric field is applied.

• The mobility of these ions in solution is influenced by their size and the strength of their solvation shells.
• This movement underpins many practical applications, such as batteries and electrolysis processes.

Understanding the properties of aqueous solutions can provide insights into chemical behavior, from simple reactions to complex biological processes.

Electric Field

An electric field is a region around a charged particle or object where other charged particles experience a force. In the context of ionic solutions, an electric field can influence the movement of ions. When alkali metal ions like \( ext{Li}^{+}\), \( ext{Na}^{+}\), \( ext{K}^{+}\), and \( ext{Rb}^{+}\) are present in an aqueous solution, the application of an electric field will cause these ions to migrate according to their charge.

• Positively charged ions (cations) will move towards the negative electrode (cathode).
• The rate of movement is influenced by ionic mobility, which is determined by both the ion size and the degree of solvation.

This principle plays a crucial role in electrochemical cells, where the movement of ions contributes to the generation of electricity. Understanding the impact of an electric field on ionic mobility can lead to advancements in developing more efficient energy storage and processing systems.