Question

List the sulfates of the Group \(2 \mathrm{~A}\) metals in order of increasing solubility in water. Explain the trend. (Hint: You need to consult a chemistry handbook.)

Short answer

Sulfate solubility order in increasing order is: BaSO₄, SrSO₄, CaSO₄, MgSO₄, BeSO₄. Solubility decreases down the group due to lattice energy changes.

Step-by-step solution

Identify the Group 2A Metals

Group 2A elements, also known as the alkaline earth metals, include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba). These are the metals concerned in this exercise.

Understand Solubility of Sulfates

Solubility refers to how well a substance (solute) dissolves in a solvent. For sulfates of Group 2A metals, the solubility trend is influenced by lattice energy and hydration energy. As you move down the group, lattice energy decreases, making sulfates less soluble; however, other factors also influence this trend.

List the Solubility Order

In general, for Group 2A metal sulfates, solubility in water decreases down the group. Thus, the order of increasing solubility in water is: 1. Barium sulfate (BaSO₄) - least soluble 2. Strontium sulfate (SrSO₄) 3. Calcium sulfate (CaSO₄) 4. Magnesium sulfate (MgSO₄) 5. Beryllium sulfate (BeSO₄) - most soluble.

Explain the Trend

The trend in solubility of Group 2A sulfates is due to a balance between lattice energy and hydration energy. Lattice energy decreases down the group, reducing the energy needed to separate the ions in the solid. However, hydration energy, which is the energy released when ions are surrounded by water molecules, does not decrease as rapidly. This results in a decrease in solubility as the heavier sulfates do not dissolve as easily.

Key concepts

Solubility Trend

The solubility of a compound is how well it dissolves in a solvent, such as water. For Group 2A metal sulfates, there is a clear trend in their solubility as you move down the group. Starting from Beryllium sulfate, which is the most soluble, to Barium sulfate, which is the least soluble. This trend can be summarized as:

• Beryllium sulfate (most soluble)
• Magnesium sulfate
• Calcium sulfate
• Strontium sulfate
• Barium sulfate (least soluble)

This order follows a general pattern of decreasing solubility. The solubility trend is important because it shows how changes in metal properties affect the behavior of the sulfates when interacting with water. Such information is valuable in both industrial applications and everyday chemical understanding.

Lattice Energy

Lattice energy is the energy required to separate the ions in a compound. For Group 2A metal sulfates, the lattice energy decreases down the group. This means it's easier to separate the ions for larger and heavier metal ions compared to the smaller ones. However, this ease of separation doesn't directly translate to increased solubility.
For example, in Beryllium sulfate, the lattice energy is quite high due to its small ionic size, making the ions close together with strong attractive forces. Although the lattice energy decreases when moving down to Barium sulfate, its solubility does not increase because other factors like hydration energy play significant roles.
Understanding lattice energy helps in predicting not only the solubility but also the stability of ionic compounds in solutions. Changes in lattice energy impact how these compounds dissolve, signify their uses, and determine their reactions in different environments.

Hydration Energy

Hydration energy is the energy released when ions are surrounded by water molecules. This energy is crucial for dissolving substances in water. In Group 2A metal sulfates, hydration energy does not decrease as significantly down the group as lattice energy does.
Hydration energy helps offset the lattice energy required to break down the structure of the solid. For smaller ions like Beryllium sulfate, the hydration energy is high, which promotes higher solubility. However, for larger ions like Barium sulfate, even though the lattice energy is lower, the lower hydration energy results in decreased solubility.
In essence, hydration energy balances lattice energy's effects, making it a pivotal factor in determining solubility trends. Realizing the role of hydration energy can help in predicting a compound's ability to dissolve and consequently, its reactivity in aqueous solutions.

Alkaline Earth Metals

Alkaline earth metals are the elements located in Group 2A of the periodic table, including Beryllium, Magnesium, Calcium, Strontium, and Barium. They are typically shiny, silvery-white metals with good conductivity for electricity.
These metals are known for forming basic (alkaline) solutions when reacting with water and for their significant roles in various chemical reactions. Their properties such as atomic size, ionic radius, and electronegativity change down the group, impacting their reactivity and the behavior of their compounds, like sulfates.
Understanding alkaline earth metals is essential because the characteristics of these metals directly influence the solubility and stability of their compounds. Knowledge of these metals' chemical and physical properties provides insights into their applications in industries such as electronics, construction, and even medicine. By learning about these elements, we gain better insight into their diverse uses and their significance in the natural world.