# Salt solubility problems and solutions

1. What is meant by the term solubility? Solution: Solubility refers to the maximum amount of a solute that can be dissolved in a specific amount of solvent at a given temperature.

2. What factors affect the solubility of a salt? Solution: The solubility of a salt is affected by several factors including temperature, pressure (for gases), and the nature of the solvent.
3. How does increasing temperature generally affect the solubility of most salts? Solution: For most salts, solubility increases with increasing temperature.
4. Why does the solubility of some salts decrease with increasing temperature? Solution: For a few salts, the solubility decreases with increasing temperature. This is because the dissolution process for these salts is exothermic, and according to Le Chatelier’s principle, the system shifts in the direction that reduces the effect of the temperature increase, i.e., towards the undissolved salt.
5. Write the solubility product expression for the salt AgCl. Solution: The solubility product expression for AgCl is Ksp = [Ag⁺][Cl⁻].
6. If the solubility of PbCl₂ in water is 1.0 x 10⁻² M at 25°C, what is its Ksp? Solution: The solubility product constant (Ksp) for PbCl₂ can be calculated using the equation Ksp = [Pb²⁺][Cl⁻]². Given that the solubility is 1.0 x 10⁻² M, each ion’s concentration is the same. So, Ksp = (1.0 x 10⁻²)(1.0 x 10⁻²)² = 1.0 x 10⁻⁶.
7. How does the common ion effect influence the solubility of a salt? Solution: The common ion effect decreases the solubility of a salt. If a solution already contains one of the ions in the salt, the additional ion from the salt will shift the equilibrium to the left according to Le Chatelier’s principle, resulting in less of the salt dissolving.
8. What is the effect of a complex ion formation on the solubility of a salt? Solution: The formation of a complex ion increases the solubility of a salt. This is because the complex ion removes one of the ions of the salt from the solution, shifting the dissolution equilibrium to the right and allowing more salt to dissolve.
9. How does pH affect the solubility of a salt that contains a basic ion? Solution: The solubility of a salt that contains a basic ion increases in an acidic solution. This is because the H⁺ ions from the acid react with the basic ions, removing them from the solution and shifting the equilibrium to allow more of the salt to dissolve.
10. How does pH affect the solubility of a salt that contains an acidic ion? Solution: The solubility of a salt that contains an acidic ion increases in a basic solution. This is because the OH⁻ ions from the base react with the acidic ions, removing them from the solution and shifting the equilibrium to allow more of the salt to dissolve.
11. What is meant by the term “solubility product constant” (Ksp)? Solution: The solubility product constant (Ksp) is the equilibrium constant for the dissolution of a salt. It is the product of the concentrations of the ions of the salt, each raised to the power of its stoichiometric coefficient in the dissolution equation.
12. Why is AgCl less soluble in water than NaCl? Solution: AgCl is less soluble in water than NaCl because the Ksp of AgCl is much smaller than that of NaCl. This indicates that the equilibrium for the dissolution of AgCl is more towards the undissolved salt.
13. If the solubility of AgBr in water is 5.0 x 10⁻⁷ M at 25°C, what is its Ksp? Solution: The solubility product constant (Ksp) for AgBr can be calculated using the equation Ksp = [Ag⁺][Br⁻]. Given that the solubility is 5.0 x 10⁻⁷ M, each ion’s concentration is the same. So, Ksp = (5.0 x 10⁻⁷)(5.0 x 10⁻⁷) = 2.5 x 10⁻¹³.
14. How can you predict the solubility of a salt based on its Ksp? Solution: The higher the Ksp, the more soluble the salt. A salt with a larger Ksp will have a greater solubility because the equilibrium for its dissolution is more towards the dissolved ions.
15. What is the effect of adding NaCl to a saturated solution of AgCl? Solution: Adding NaCl to a saturated solution of AgCl decreases the solubility of AgCl due to the common ion effect. The added Cl⁻ ions shift the equilibrium to the left, resulting in the precipitation of AgCl.
16. How does pressure affect the solubility of a salt? Solution: Pressure has little effect on the solubility of solids and liquids, including salts, but increases the solubility of gases in liquids.
17. Why is it important to consider the solubility of salts in environmental studies? Solution: It’s important because many salts can affect the physical and chemical properties of the environment. For instance, salts that are highly soluble can contaminate water resources and soils, leading to problems for plants, animals, and humans.
18. What is the effect of adding a chelating agent like EDTA to a solution of a metal ion? Solution: Adding a chelating agent like EDTA to a solution of a metal ion increases the solubility of the metal salt. The EDTA forms a complex ion with the metal ion, removing it from the solution and shifting the equilibrium to allow more of the salt to dissolve.
19. What is the principle behind the method of adding a suitable reagent to a solution to reduce the solubility of a particular ion? Solution: This method is based on the principle of selective precipitation. A reagent is added that forms a sparingly soluble compound with the particular ion, reducing its solubility and causing it to precipitate from the solution.
20. How does the solubility of a salt in a given solvent relate to its lattice energy and the hydration energy of its ions? Solution: The solubility of a salt is determined by the balance between its lattice energy, which must be overcome for the salt to dissolve, and the hydration energy of its ions, which is released when the ions are surrounded by water molecules. If the hydration energy is greater than the lattice energy, the salt will dissolve; otherwise, it will remain undissolved.