Question

The conductivity of a strong electrolyte : (a) Increases on dilution (b) Decreases on dilution (c) Does not change with dilution (d) Depends upon density of electrolytes

Short answer

Increases on dilution.

Step-by-step solution

Understand what a strong electrolyte is

A strong electrolyte is a solute that completely or nearly completely ionizes or dissociates in a solution. The ions carry electric current through the solution, making it conductive.

Consider the effect of dilution

On dilution, the number of ions per unit volume decreases, but the total number of ions remains the same since complete dissociation occurs. Thus, the ability to carry current decreases, meaning conductivity decreases.

Relate conductivity to dilution

Conductivity is directly proportional to the number of ions present in the solution. As a solution is diluted, ion concentration decreases, which lowers the conductivity.

Key concepts

Electrolyte Dilution

When it comes to understanding the behavior of strong electrolytes in solutions, 'electrolyte dilution' is a fundamental concept. Strong electrolytes, such as salts, acids, and bases, dissociate completely into ions when dissolved in water. The process of dilution involves adding more solvent, usually water, to a solution, which results in a decrease in the concentration of ions per unit volume.

As a solution is diluted, the ions become more spread out. This is important because the degree of ion separation affects many properties of the solution, including its conductivity. Although the total number of ions remains unchanged, the reduced concentration of ions leads to a decrease in the solution’s ability to conduct electricity. Here's why: if you imagine passing an electric current through the solution, the current is carried by the ions moving through the solvent. With fewer ions in a given volume, there will be less charge transport, and thus, lowered conductivity.

To delve a bit deeper, consider a cup of salty water. If you were to add more water to the cup, the salt (a strong electrolyte) would still be completely ionized, but the ions would be less densely packed. Consequently, the electric current would have to travel further between ions, making the process less efficient and resulting in lower conductivity.

Ionization of Electrolytes

Understanding the 'ionization of electrolytes' provides insight into why the conductivity of strong electrolytes increases or decreases. Ionization is the process by which an electrolyte, upon dissolving in a solvent, splits into constituent ions. Strong electrolytes are characterized by their ability to ionize completely, which means they disassociate into their positive and negative ions entirely in a solution.

Each ion becomes surrounded by solvent molecules in a process known as solvation, which stabilizes the ions in solution and prevents them from recombining into the non-ionized state. The complete ionization of strong electrolytes explains their high levels of conductivity as they produce a large number of charged particles capable of carrying an electric current. When a strong electrolyte is dissolved in water, it creates a uniformly conductive solution because the ions disperse evenly throughout.

For instance, when table salt (sodium chloride, NaCl) dissolves in water, it dissociates into sodium (Na⁺) and chloride (Cl⁻) ions, which are then free to move and carry current in the solution. This quality makes strong electrolytes distinct from weak electrolytes, which only partially dissociate in solution, resulting in lower conductivity.

Electrolytic Conductivity

The concept of 'electrolytic conductivity' is integral in understanding how electric currents pass through ionic solutions. Electrolytic conductivity refers to the measure of a solution's ability to conduct electricity. It is highly dependent on the presence and mobility of ions within the solution – more ions and higher mobility mean better conductivity.

In the context of strong electrolytes, since they disassociate into ions completely, they typically show high conductivity. However, this conductivity is not static and will vary depending on several factors, such as the concentration of ions, which is influenced by dilution, and the temperature of the solution. Higher temperatures generally increase ion mobility, which increases conductivity.

Conductivity is often measured using a conductivity meter, which calculates the ease with which an electric current can pass through a solution. The meter measures the electrical current that flows between two electrodes placed in the solution. The reading is directly proportional to the concentration of ions – the greater the number of freely moving charge carriers (ions), the higher the conductivity. Therefore, in a diluted solution of a strong electrolyte, as the concentration of ions per unit volume decreases, so does the electrolytic conductivity.