Question

Shown below is a representation of the ionic solid \(\mathrm{MX}\), where \(\mathrm{M}\) cations are represented by squares and \(X\) anions are represented by circles. Fill in the box after the arrow to represent what happens to the solid after it has been completely dissolved in water. For simplicity, do not represent the water molecules.

Short answer

Answer: When the ionic solid MX is dissolved in water, it dissociates into its constituent M cations and X anions due to the polar nature of water molecules.

Step-by-step solution

Identify the ionic solid MX

The ionic solid MX is made up of M cations (squares) and X anions (circles). When the solid is dissolved in water, the cations and anions will separate due to the polar nature of water molecules.

Visualize the dissolution process

When the ionic solid MX is dissolved in water, the M cations and X anions will be attracted to the polar water molecules. This causes the ionic solid to dissociate into its constituent ions. In this step, we will represent the ions after the dissolution without representing water molecules: Original solid: M X X M After dissolution without water molecules: M X X M

Fill in the box after the arrow

Now that the dissolution has been visually represented, fill in the box after the arrow with the dissociated ions: Original solid: M X X M Arrow (→) Dissolved solid without water molecules: M X X M

Key concepts

ionic solids

Ionic solids are fascinating structures made up of charged particles. Think of them as a closely packed collection of cations and anions. These oppositely charged ions are bound together by strong electrostatic forces, which is why ionic solids are typically hard and have high melting points.
They often form fascinating crystal lattices where each cation is surrounded by anions and each anion is surrounded by cations, creating a repeating three-dimensional pattern. However, their ionic bonds make them brittle, and it only takes a slight shift in the lattice to cause a break.
When you dissolve an ionic solid in water, these electrostatic bonds are broken, and the solid breaks down into its individual ions. This process is essential for various chemical reactions and plays a crucial role in the conductivity of solutions. Ionic dissociation is intrinsic to how salts dissolve and dissolve into their constituent ions, an important aspect of chemistry.

dissociation process

The dissociation process is the method through which an ionic solid separates into its individual ions. This occurs most commonly when the solid is introduced to a solvent like water. The process is initiated because water molecules, which are polar, are more attractive than the ionic bonds holding the solid together.
When an ionic solid is dropped into water, its ions begin to disperse. The polar water molecules are drawn to the charged ions due to their opposite charges, helping to pull the ions away from each other and overcoming the ionic bond.
The original structure of the solid alters: cations and anions become solvated, meaning they are surrounded by water molecules. This interaction significantly weakens the ionic bonds, allowing the solid to completely dissociate into free-moving ions capable of conducting electricity, which is why ionic solutions are good conductors.

polar molecules

Polar molecules are a key player in the dissolution of ionic solids. They have an uneven distribution of charge across their molecular structure, which means they have both a slightly positive end and a slightly negative end. Water is the most common example of a polar molecule, thanks to its bent shape and the difference in electronegativity between the hydrogen and oxygen atoms.
When an ionic solid like MX is placed in water, the polar molecules act like a mediator. The positively charged end of the water molecule will attract the negatively charged anions, while the negatively charged end will attract the positively charged cations.
This attraction initiates the breakdown of the ionic solid, pulling ions away from their lattice and into the solution. As a result, the solid dissolves, and its ions disperse throughout the solvent. This property of polar molecules is what makes them so essential in chemical analysis, biochemical processes, and everyday life when using solvents.