Question

Which of the following schematic drawings best describes a solution of \(\mathrm{Li}_{2} \mathrm{SO}_{4}\) in water (water molecules not shown for simplicity)? [Section 4.1]

Short answer

The correct schematic drawing for a solution of Li₂SO₄ in water depicts dissociated lithium ions (Li⁺) and sulfate ions (SO₄²⁻) distributed throughout the solution. The dissociation of Li₂SO₄ can be represented as: \[ \mathrm{Li}_{2}\mathrm{SO}_{4} \rightarrow 2\mathrm{Li}^{+} + \mathrm{SO}_{4}^{2-} \] Review the given drawings and choose the one showing the separated Li⁺ ions and SO₄²⁻ ions, keeping in mind that water molecules are not shown for simplicity.

Step-by-step solution

Write the Dissociation Equation of Li₂SO₄

Write the chemical equation for the dissociation of Li₂SO₄ in water. When Li₂SO₄ is dissolved in water, it dissociates into its constituent ions. In this case, lithium ions (Li⁺) and sulfate ions (SO₄²⁻) are produced. The chemical equation for the dissociation of Li₂SO₄ in water is: \[ \mathrm{Li}_{2}\mathrm{SO}_{4} \rightarrow 2\mathrm{Li}^{+} + \mathrm{SO}_{4}^{2-} \]

Identify the Ions in the Solution

Identify the ions present in the Li₂SO₄ solution. From the dissociation equation in Step 1, we can see that there will be lithium ions (Li⁺) and sulfate ions (SO₄²⁻).

Review the Schematic Drawings

Review each of the given schematic drawings and identify the one which best represents the dissociation of Li₂SO₄ in water. To identify the correct drawing, look for the presence of both lithium ions (Li⁺) and sulfate ions (SO₄²⁻) in the solution, and check if they are properly dissociated (i.e., not bound together). Remember that water molecules are not shown for simplicity.

Select the Correct Drawing

Choose the schematic drawing that best describes the Li₂SO₄ solution in water, according to the criteria established in Step 3. The correct drawing should clearly show dissociated lithium ions (Li⁺) and sulfate ions (SO₄²⁻) distributed in the solution. After comparing all the schematic drawings, the correct drawing can be identified, and the exercise is complete.

Key concepts

Electrolyte Dissolution

Understanding the dissolution of electrolytes in water is crucial for comprehending many chemical processes. An electrolyte is a compound that produces ions when dissolved in water, thus allowing the solution to conduct electricity.

The dissolution process involves the breaking apart of the crystalline structure of the ionic compound as each ion is surrounded by water molecules. This interaction between the water molecules and the ions is due to the polarity of water, which facilitates the separation of the ions.

Effects of Dissolving Electrolytes

When dissolved, electrolytes such as \( \mathrm{Li}_{2} \mathrm{SO}_{4} \) separate into their constituent ions. This separation allows various chemical reactions to occur in solution, including those important in biological systems and industrial applications.

For instance, in the case of dissolving \( \mathrm{Li}_{2} \mathrm{SO}_{4} \), lithium ions \( \mathrm{Li}^{+} \) and sulfate ions \( \mathrm{SO}_{4}^{2-} \) are formed. Each of these ions becomes solvated, meaning water molecules cluster around the ion, stabilizing it in solution.

It's important to note that not all ionic compounds dissolve in water. The solubility of an electrolyte depends on various factors, including temperature and the presence of other ions in the solution.

Chemical Equation Writing

Writing chemical equations is a key skill in understanding chemical processes. It represents with symbols and formulas, the reactants, products, and direction of a chemical reaction. When we write the equation for the dissociation of an ionic compound like \( \mathrm{Li}_{2} \mathrm{SO}_{4} \), we need to show both the reactant (the ionic compound) and the products (the ions).

Steps for Writing Dissociation Equations

A proper dissociation equation should balance both the number of atoms and the overall charge. For \( \mathrm{Li}_{2} \mathrm{SO}_{4} \), the equation must reflect the production of lithium ions and sulfate ions in water, represented as \[ \mathrm{Li}_{2}\mathrm{SO}_{4} \rightarrow 2\mathrm{Li}^{+} + \mathrm{SO}_{4}^{2-} \].

This indicates that one molecule of \( \mathrm{Li}_{2} \mathrm{SO}_{4} \) yields two lithium ions and one sulfate ion upon dissolution. Students should carefully check the subscripts and charge balances to ensure accuracy.

It's essential to include the state of each substance (solid, liquid, gas, or aqueous) in the equation, although this is often omitted in schematic representations for simplicity. The equation writing process is vital for understanding the nature of the dissolved species and for predicting the outcomes of reactions in solution.

Ions in Solution

Ions in solution are the result of the dissociation of electrolytes, such as salts, acids, and bases, in water. These ions are the carriers of electric charge within the solution, making it conductive.

Behavior of Ions in Solution

Once in solution, ions will interact with each other and with the solvent. Their behavior is influenced by several factors, including concentration, types of ions, and the presence of other substances.

For instance, in the dissolution of \( \mathrm{Li}_{2} \mathrm{SO}_{4} \) in water, we primarily focus on lithium ions \( \mathrm{Li}^{+} \) and sulfate ions \( \mathrm{SO}_{4}^{2-} \). These ions are free to move in the solution, which allows them to conduct electricity and participate in further chemical reactions.

Students must recognize not just the presence of these ions but also their ratio, as reflected by the chemical equation of their dissolution. For every mole of \( \mathrm{Li}_{2} \mathrm{SO}_{4} \) dissolved, there will be twice as many moles of \( \mathrm{Li}^{+} \) ions compared to \( \mathrm{SO}_{4}^{2-} \) ions. This stoichiometric relationship is crucial for understanding the quantitative aspects of chemical solutions.