Question

The Hittorf's rule states that (a) the loss of concentration around any electrode is proportional to the speed of the ions moving towards it (b) the loss of concentration around any electrode is proportional to the speed of the ions moving away from it (c) the loss of concentrations around both the electrodes is proportional to the sum of speed of cations and anions (d) none of the above

Short answer

The correct statement about Hittorf's rule is (a) the loss of concentration around any electrode is proportional to the speed of the ions moving towards it.

Step-by-step solution

Understand Hittorf's Rule

Hittorf’s rule states that during electrolysis, the change in concentration of an electrolyte near an electrode is proportional to the velocity of the ion moving towards it.

Review the choices

(a) says the loss of concentration around any electrode is proportional to the speed of the ions moving towards it, which matches Hittorf's rule.\n(b) suggests the ions are moving away, which contradicts the rule.\n(c) proposes a combination of ions moving towards both electrodes, which is not specified in Hittorf's rule.\n(d) claims none of the above. If (a) is correct, this would not be the case.

Select the correct statement

From the understanding of Hittorf’s rule, the correct statement would be (a), as it accurately represents the rule.

Key concepts

Understanding Electrolysis

Electrolysis is a fascinating and important chemical process in which electric current is used to drive an otherwise non-spontaneous chemical reaction. Central to this process are two electrodes: the cathode, which attracts cations, and the anode, which attracts anions. A solution or molten substance called the electrolyte contains ions that move to the electrodes when an electric current is applied, resulting in the gain or loss of electrons and leading to the formation of new substances at the electrodes.

As an example, consider the electrolysis of aqueous sodium chloride (table salt). When a direct electric current passes through the water, chloride ions migrate towards the anode to form chlorine gas, while sodium ions move to the cathode and react with water to produce sodium hydroxide and hydrogen gas. This example clearly illustrates how the flow of electricity brings about a transformation of materials through the movement and reaction of ions.

Ion Concentration Change During Electrolysis

During the process of electrolysis, ion concentration change is a key phenomenon that occurs in the vicinity of the electrodes. As ions are either deposited onto the electrode or incorporated into newly formed compounds, their concentrations near the electrode surface change. Hittorf's rule helps us understand this change by stating that the change in concentration is directly proportional to the velocity of the ions as they move towards an electrode.

For instance, in the electrolysis of copper sulfate with copper electrodes, the concentration of Cu²⁺ ions near the cathode decreases as these ions gain electrons and become solid copper. Unlike a static situation, the dynamic nature of electrolysis means that both the concentration and distribution of ions in the solution are continually altered as electrolysis proceeds. Careful analysis and understanding of these changes can be crucial for optimizing industrial electrolytic processes, such as the refining of metals or the manufacturing of chemical compounds.

Ion Velocity's Role in Electrolysis

The concept of ion velocity is integral to comprehending how electrolysis progresses. Ion velocity refers to the speed at which ions move through the electrolyte towards an electrode. This movement is influenced by several factors, including the electrical potential applied across the electrodes, the nature of the ion (its charge and size), and the conductivity of the electrolyte.

Moreover, the velocity of an ion affects how quickly the concentration changes at the respective electrode, as suggested by Hittorf's rule. Higher ion velocities result in greater changes in concentration over a given time period, illustrating a direct relationship between the rate of ion movement and the observable changes in an electrolytic solution. In practice, understanding and controlling ion velocity is crucial for various applications, such as electroplating, where consistent ion deposition rates are necessary to ensure a uniform and high-quality metallic coating.