Question

Lithium fluoride (LiF) is a strong electrolyte. What species are present in \(\mathrm{LiF}(a q) ?\)

Short answer

The species present are \( \mathrm{Li}^{+} \) and \( \mathrm{F}^{-} \) ions.

Step-by-step solution

Understanding the Compound

Lithium fluoride, \( \mathrm{LiF} \), is a chemical compound composed of lithium ions \( \mathrm{Li}^{+} \) and fluoride ions \( \mathrm{F}^{-} \). It is an ionic compound.

Dissociation in Water

When LiF is dissolved in water to form an aqueous solution, it dissociates completely into its ions. This is because it is a strong electrolyte.

Identifying the Ions

The dissociation of \( \mathrm{LiF} \) in water results in the formation of lithium ions (\( \mathrm{Li}^{+} \)) and fluoride ions (\( \mathrm{F}^{-} \)). These are the species present in the solution.

Key concepts

Ionic Compounds

Ionic compounds are chemical compounds formed by the transfer of electrons between atoms, resulting in the creation of ions. These ions are atoms with a net electrical charge due to the loss or gain of electrons. Typically, this occurs between metals and non-metals. The metal atoms tend to lose electrons and become positively charged cations, while the non-metal atoms gain electrons to become negatively charged anions.
Ionic compounds, like lithium fluoride (\(\text{LiF}\)), have a crystalline structure due to the strong electrostatic forces that hold the ions together in a lattice. This structure gives them certain properties such as high melting points and good electrical conductivity when dissolved in water. They are often observed as crystalline solids at room temperature.

Dissociation in Water

Dissociation in water is a crucial process for ionic compounds like lithium fluoride. When an ionic compound dissolves in water, it separates into its constituent ions. This process is referred to as dissociation.
For a strong electrolyte like \(\text{LiF}\), the dissociation is complete, meaning that the compound fully separates into lithium ions (\(\text{Li}^+\)) and fluoride ions (\(\text{F}^-\)). These ions become surrounded by water molecules, a phenomenon called hydration, which stabilizes them in the solution. Because the ions are free to move, the solution can conduct electricity efficiently, which is a hallmark of a strong electrolyte.

Lithium Fluoride (LiF)

Lithium fluoride is a simple binary ionic compound consisting of lithium and fluoride ions. It is known for its strong ionic bonds, which result from the transfer of an electron from the lithium atom to the fluoride atom. This electron transfer is what makes lithium a positively charged ion (\(\text{Li}^+\)) and fluoride a negatively charged ion (\(\text{F}^-\)).
Lithium fluoride is commonly encountered as a white, crystalline solid. Due to its strong ionic bonds, it has high melting and boiling points, and it is not very soluble in water compared to other alkali metal halides. However, once it dissolves, its ions dissociate completely, leading to its characterization as a strong electrolyte.

Ion Formation

Ion formation is a process where atoms gain or lose electrons to form ions. This process is pivotal in the formation of ionic compounds. In the case of lithium fluoride, ion formation occurs when lithium, a metal, donates its lone electron to fluoride, a non-metal.
This electron transfer results in the formation of two ions:

• Lithium Ion (\(\text{Li}^+\)): This occurs because lithium loses one electron, resulting in a positive charge due to an excess of protons compared to electrons.
• Fluoride Ion (\(\text{F}^-\)): Fluoride gains an electron, resulting in a negative charge because of an excess of electrons compared to protons.

These ions are what allows the ionic compound to dissolve and form a solution that conducts electricity when added to water.