Question

When asked what causes electrolyte solutions to conduct electricity, a student responds that it is due to the movement of electrons through the solution. Is the student correct? If not, what is the correct response?

Short answer

The student's response is incorrect. Electrolyte solutions conduct electricity due to the movement of ions (both positively charged cations and negatively charged anions) in the solution, not the movement of electrons. The ions act as charge carriers, allowing the solution to conduct electricity.

Step-by-step solution

Analyzing the student's response

The student claims that electrolyte solutions conduct electricity due to the movement of electrons through the solution.

Understanding electrolyte solutions

An electrolyte solution is a solution that contains dissolved ions. When a solid electrolyte dissolves in a solvent, it usually separates into positively charged ions (cations) and negatively charged ions (anions). These ionized particles are free to move in the solution, making the solution conductive.

Evaluate the student's response

The student's response about electron movement through the solution is incorrect. In an electrolyte solution, it's not the movement of electrons that causes it to conduct electricity, but the movement of ions (both cations and anions) that carry the electric charge.

Provide the correct response

The correct response: Electrolyte solutions conduct electricity due to the movement of ions (both positively charged cations and negatively charged anions) in the solution, not the movement of electrons. The ions act as charge carriers, allowing the solution to conduct electricity.

Key concepts

Electrical Conductivity

Electrical conductivity is the measure of a material's ability to allow the flow of electric current. For a solution to be electrically conductive, it must have charge carriers that can move freely when a voltage is applied. In the case of electrolyte solutions, these charge carriers are not electrons, as one might initially assume, but ions that are produced when a substance dissociates in water. The movement of these ions in opposite directions under the influence of an electric field leads to the conduction of electricity. To visualize this, imagine placing a battery with a positive and a negative terminal into an electrolyte solution. The cations will move towards the negative terminal, whereas the anions move towards the positive terminal, creating a flow of electrical charge that constitutes an electric current.

Ions in Solution

When an electrolyte dissolves in water, the result is a solution full of ions, which are atoms or molecules that have lost or gained electrons, giving them a net charge. These ions are essential for the conductivity of the solution. In solution, ions are surrounded by water molecules, which stabilize them and allow them to move freely. This state of being surrounded by water molecules is called hydration. The ease with which this substance dissolves and forms ions dictates its ability to create an electrolyte solution. Some compounds, like table salt (NaCl), readily dissolve and dissociate completely into Na+ and Cl- ions. This complete dissociation into ions is why solutions like salt water are good conductors of electricity.

Cations and Anions

Ions can be broadly classified into two categories: cations and anions. Cations are positively charged ions, which result from the loss of one or more electrons. An example of a cation is a sodium (Na+) ion. On the other hand, anions are negatively charged ions, formed by the gain of one or more electrons, like the chloride (Cl-) ion. The balance between cations and anions in solution is crucial; it maintains electric neutrality in the solution. Despite their charge, neither cations nor anions should be confused with free electrons; their movement does not constitute the flow of electrons as would be seen in metal conductors but rather the transport of electric charge in ionic form.

Electric Charge Carriers

Electric charge carriers are the particles that transport electric charge within a conductor when an electric field is applied. In metallic conductors, such as copper wires, electrons are the charge carriers. When discussing electrolyte solutions, however, the charge carriers are the mobile ions in the solution. Cations, carrying a positive charge, move towards the cathode (negative electrode), and anions, with a negative charge, move towards the anode (positive electrode). This ionic migration across the solution enables an electric current to pass through the solution, thereby demonstrating that the solution is capable of conducting electricity. This concept corrects the common misconception that electron transfer is necessary for electrical conductivity in all substances, emphasizing the role of ions as charge carriers in electrolyte solutions.