What are Solutions and Solubilities?
A solid, liquid or gaseous chemical material to dissolve in a solvent and form a solution is known as solubility. The entire phenomena are called solutions and solubilities. A substance's solubility is largely determined by the solvent used, as well as temperature and pressure. The saturated solution concentration is used to determine a substance's solubility in a given solvent. When adding more solute to a solution does not increase the concentration of the solution, it is said to be saturated. The degree of solubility varies greatly between substances, ranging from infinitely soluble (fully miscible) ethanol in water to poorly soluble silver chloride in water. Poorly soluble compounds are sometimes referred to as "insoluble." The equilibrium solubility can be surpassed under such conditions, resulting in a supersaturated solution.
Factors Affecting Solutions and Solubilities
Temperature
In solutions and solubilities, the solubility rises as the temperature rises. This is true for the majority of solvents. Gases, on the other hand, are in a different condition. They became less soluble in each other and in water as the temperature rose, but more soluble in organic solvents.
Polarity
Solutes dissolve in solvents with equal polarity in the vast majority of cases. To explain this property of solutes and solvents, chemists use the aphorism "Like dissolves like." Polar solvents do not dissolve nonpolar solutes and vice versa.
Pressure
Solid and Liquid Solutes
Pressure has little effect on the solubility of the majority of solid and liquid solutes.
Gas Solutes
In the case of gases, Henry's law states that the solubility of a gas is directly proportional to its pressure. This is expressed mathematically as p = kc, where k is a temperature-dependent gas constant. When opening a bottle of carbonated beverage, a clear example of Henry's law can be seen. As the pressure in a bottle is reduced, the gas dissolved in the drink bubbles to the surface.
Stirring Increases the Speed of Dissolving
We could dissolve the sugar in the tea if we let it sit for long enough. Stirring only speeds up the process by increasing the movement of the solvent, which introduces the solute to new parts of it, allowing for solubility. Since molecules in liquid fluids are constantly moving, the process will occur anyway, but it would take longer.
Types of Solubility
The solvent is the substance present in the greatest quantity in all liquids, whether gaseous, liquid, or solid, and the solute is the substance or substances present in smaller quantities (s). While the solute does not have to be in the same physical state as the solvent, the solvent's physical state normally decides the solution's state. The solute is assumed to be soluble in the solvent if the solute and solvent combine to form a homogeneous solution.
Forming a Solution
A physical process, not a chemical one, results in the forming of a solution from a solute and a solvent. That is, effective separation methods will recover both the solute and the solvent in chemically unchanged forms. Strong zinc nitrate, for example, dissolves in water to form an aqueous zinc nitrate solution:
Zn(NO3)2(s)+H2O(l)→Zn2+(aq)+2NO−3(aq)(13.2.1)
This is a physical method since Zn(NO3)2 can be quickly retrieved by evaporating the water. Metallic zinc, on the other hand, fails to dissolve in aqueous hydrochloric acid. In fact, the two substances react chemically to form a zinc chloride aqueous solution with the release of hydrogen gas:
Zn(s)+2H+(aq)+2Cl−(aq)→Zn2+(aq)+2Cl−(aq)+H2(g)(13.2.2)
We don't get metallic zinc back when the solution evaporates, so we can't tell it's soluble in aqueous hydrochloric acid because it's chemically converted when it dissolves. A chemical transition does not occur when a solute dissolves in a solvent to form a solution (that it is a physical change).
A chemical transition does not occur when a solute dissolves in a solvent to form a solution.
The term "fully miscible" refers to substances that form a single homogeneous phase in all proportions. Ethanol and water are miscible in the same way that gas mixtures are.
Immiscible means that two substances are essentially insoluble in each other, such as oil and water. The Earth's atmosphere is an example of a gaseous solution that we have already discussed.
Fun Facts
When one material is fully dissolved in another, it is called a solution. You can create a solution by mixing sugar and water, for example. The faster the solvent mixes with water, the higher is the solubility of water.
When you add two things, but they don't fully blend, you get a mixture. For example, if you put sand in a cup of water, it will sink to the bottom.
FAQs on Solutions and Solubilities
1. What is a solution, and how is solubility defined in chemistry?
A solution is a homogeneous mixture of two or more substances. The substance that gets dissolved is called the solute, and the substance it dissolves in is the solvent. Solubility, on the other hand, is a specific measurement. It defines the maximum amount of a solute that can be dissolved in a given amount of solvent at a specific temperature to form a saturated solution.
2. What is the main difference between a saturated and an unsaturated solution?
The main difference lies in how much solute they contain relative to their limit. An unsaturated solution is one that can still dissolve more solute at a given temperature. In contrast, a saturated solution has reached its equilibrium point; it contains the maximum amount of dissolved solute possible at that temperature, and any extra solute added will not dissolve.
3. What are the key factors that affect the solubility of a substance?
Several factors can change how much of a substance dissolves. The most important ones are:
- Temperature: For most solid solutes, solubility increases as temperature increases. However, for gases, solubility in liquids decreases as temperature rises.
- Pressure: This factor primarily affects the solubility of gases in liquids. According to Henry's Law, higher pressure increases the solubility of a gas.
- Nature of Solute and Solvent: This is based on the chemical principle of "like dissolves like." Polar solutes like salt dissolve well in polar solvents like water, while non-polar solutes like oil do not.
4. What are the different types of solutions based on the physical state of the components?
Solutions can be formed from components in any physical state (solid, liquid, or gas). They are typically classified based on the state of the solvent. For example, you can have a gas dissolved in a liquid (like carbonated water), a liquid in a liquid (like vinegar in water), a solid in a liquid (like saltwater), or even a solid in a solid (like metal alloys such as brass).
5. How are the concepts of 'solution' and 'solubility' related but different?
A 'solution' is the actual mixture you create, like sugar dissolved in water. It is a general term for a homogeneous mixture. 'Solubility' is a quantitative property or a measurement that tells you *how much* sugar can possibly dissolve in the water under specific conditions to make it saturated. In short, solubility is the rule that governs the limit of a solution.
6. Why do carbonated drinks go flat faster when they are warm?
This happens because the solubility of a gas (in this case, carbon dioxide) in a liquid decreases as the temperature increases. When a carbonated drink gets warm, the dissolved CO₂ gas becomes less soluble and escapes from the liquid much more quickly. This loss of dissolved gas is what causes the drink to lose its fizz and go 'flat'.
7. Why does stirring help a solid like sugar dissolve faster in water?
Stirring does not change the total amount of sugar that can dissolve, but it greatly increases the rate of dissolving. When you add sugar, the water immediately surrounding the crystals becomes saturated quickly, slowing down the process. Stirring moves this saturated layer away and brings fresh, unsaturated solvent into contact with the sugar crystals. This allows more sugar to dissolve continuously and much faster.
8. What are colligative properties and why are they important for understanding solutions?
Colligative properties are special physical properties of solutions that depend only on the concentration of solute particles, not on the solute's identity. They are important because they explain how a solvent's physical behaviour changes when a solute is added. The main colligative properties are:
- Relative lowering of vapour pressure
- Elevation of boiling point
- Depression of freezing point
- Osmotic pressure
9. Can a solution be both saturated and dilute at the same time? Explain with an example.
Yes, a solution can be both saturated and dilute. This occurs when a substance has very low solubility. A dilute solution has a small amount of solute, while a saturated solution contains the maximum possible amount. If a substance is not very soluble, its saturation point is reached with only a tiny amount of solute. For instance, a saturated solution of silver chloride (AgCl) in water is also very dilute because so little AgCl can dissolve in the first place.
