Question

Predict and explain which of the following systems are electrically conducting: (a) solid \(\mathrm{NaCl},(\mathrm{b})\) molten \(\mathrm{NaCl}\), (c) an aqueous solution of \(\mathrm{NaCl}\).

Short answer

Molten and aqueous NaCl are conductive, while solid NaCl is not.

Step-by-step solution

Understanding Solid NaCl

Solid NaCl forms an ionic lattice structure where sodium (Na) and chloride (Cl) ions are arranged in a rigid, fixed pattern. Since the ions are immobile in a solid state, they cannot carry an electric current. Thus, solid NaCl is not electrically conductive.

Analyzing Molten NaCl

When NaCl is heated to its melting point, it becomes molten. In this liquid state, the ionic lattice breaks down, and the Na⁺ and Cl⁻ ions become free to move. Because these charged particles can now flow and carry a current, molten NaCl is electrically conductive.

Examining Aqueous NaCl Solution

In an aqueous solution of NaCl, the NaCl dissociates in water into Na⁺ and Cl⁻ ions. The polar water molecules help to dissolve and stabilize these ions, allowing them to move freely in the solution. This movement of ions facilitates the conduction of electricity. Therefore, an aqueous solution of NaCl is electrically conductive.

Key concepts

Understanding Ionic Compounds

Ionic compounds are formed when metals transfer electrons to non-metals, creating charged particles or ions. These ions form a lattice structure held together by strong electrostatic forces of attraction. A common example is sodium chloride (NaCl), where sodium (Na) donates an electron to chlorine (Cl).

These substances typically have high melting and boiling points due to the strength of the ionic bonds holding the lattice together, which requires a lot of energy to break. In their solid state, these ions are rigidly locked in place and cannot move freely. This immobility means solid ionic compounds do not conduct electricity. Conductivity requires free-moving charged particles, and in the solid form, ions are static.

However, when ionic compounds are melted or dissolved in water, this changes. We'll explore these states further in the next sections.

The Conductive Nature of Molten State

When an ionic compound like NaCl is heated to high temperatures, it reaches its molten state. In this process, the solid lattice breaks apart, and the ions are freed from their structured positions. The breakdown of this structure happens because the thermal energy provided is enough to overcome the electrostatic forces holding the ions in place.

In the molten state, these ions are no longer fixed in the lattice. They gain the ability to move around within the liquid, allowing them to carry electrical current. As a result, molten ionic compounds like NaCl are good conductors of electricity because the free ions act as charge carriers.

• High temperature melts the lattice.
• Ions become mobile.
• Free-moving ions enable electrical conductivity.

Understanding how ionic compounds behave when transitioning from solid to molten state aids in comprehending their electrical conductivity properties.

Exploring Aqueous Solution Conductivity

An aqueous solution involves dissolving a substance, like NaCl, in water. In this context, water acts as a solvent, and the solid NaCl dissociates into its component ions, Na⁺ and Cl⁻.

Water molecules have a polar nature, meaning they have a partial charge that aids in the dissociation process. The positive end of a water molecule attracts the negatively charged chloride ions, while its negative end attracts the positively charged sodium ions. This interaction helps stabilize the ions in the solution and allows them to move freely.

• Ionic lattice breaks down in water.
• NaCl dissociates into Na⁺ and Cl⁻ ions.
• Freely moving ions conduct electricity.

Aqueous solutions are thus excellent conductors of electricity due to the mobility of these dissolved ions. This ability to conduct electricity makes aqueous solutions crucial in various applications, including biological systems and chemical reactions. It is important to note that without the solvent, the ionic compounds in solid form wouldn’t exhibit any conductivity.