Solubility Definition, Rules, Tables, and FAQs

Solubility

Chemistry defines matter as everything that has a fixed mass and encompasses space. Matter exists in three states: solid, gaseous, and liquid. Physical qualities of matter include odor, form, melting and boiling point, and solubility. Now the question arises, what is solubility, and how is it a physical quality of the matter? 

A mixture, i.e., a solution, is formed when a gas or a solid is completely mixed into a liquid. If a solid completely dissolves and disappears in a liquid so that its particles become evenly distributed and are no longer visible, that solid can be soluble.

In this scenario, a solid is referred to as the solute, and the liquid in which it dissolves is referred to as the solvent. It can exist as a gas, a liquid, or a solid.

Did You Know? Water is regarded as the most solvent matter or liquid in chemistry; the reason behind this statement is that it can mostly dissolve any form of substance in itself.

After reading this article, students can comprehend the definition, table, rules, and factors affecting material solubility.

What is Solubility?

Definition: It is the degree to which a component can be completely dissolved in a solvent to form a solution. The solubility level of the same form of matter (for instance, liquids into liquids or gases into gases) is entirely absolute (for instance, methanol and water or oxygen and carbon dioxide). In some cases, the solution is partially solute (for instance, water and oil dissolve partially in one another).

Thus, one can say that “similar dissolves similar” in general (e.g., aromatic gases can completely dissolve into each other but not in water). The solubility of solids in liquids increases in temperature, whereas the solubility of gases decreases with temperature and increases with compression. A saturated solution is one in which no additional solute can be incorporated at a specific pressure and temperature.

Thus, to define solubility in chemistry, one can say that solubility is the maximum proportion of solid/solute that may be dissolved in a specified amount of a solvent at a specific temperature. Hence, solubility explains the characteristics, and the rate of dissolution of a solute dissolves in a solvent.

So, what does the term “solubility” signify in science? Solubility is described as a material’s capacity to combine with another substance. Solutes can be classified as soluble, partially soluble, or insoluble.

Did You Know? When combined with a solvent or liquid, insoluble solutes generate sediment or precipitate. A precipitate is created when a solid particle stays floating or suspended in a liquid, separating the solid from the liquid solution. At the same time, sediments are those solid particles that settle down or sink at the bottom of the liquid container.

Define Solubility Units

When a solute combines with a solvent, the solution produced can be either saturated, unsaturated, or supersaturated. Unsaturated solutions contain less solute and tend to absorb more solute. At the same time, a saturated solution incorporates all of the solutes and cannot further dissolve or mix any additional solutes. On the contrary, a supersaturated solution contains more solute than the solvent required to dissolve it.

It is commonly expressed in milligrams per liter (mg/L) or one gram per 100 milliliters of solvent (g/100ml). Solubility can be classified into three categories. These are soluble, partially soluble, or insoluble. A soluble solute has a solubility of more than 1g per 100 ml of solvent. In contrast, an insoluble solute has a solubility of less than 0.1g per 100 ml of solvent. Partially soluble solutes come between these two limitations.

These solubility rates apply only to solids and liquids and not to gases. For example, the solubility of oxygen in the liquid is 0.0009g per 100 ml at 20 degrees Celsius. Since this proportion of oxygen can sustain aquatic life, it is regarded as soluble. However, according to the solubility rates, if a liquid or solid has a solubility rate of 0.0009g per 100 ml, it is considered insoluble. 

Solubility Rules

There are various conceivable outcomes when a material is combined with a solvent. The result is determined by the substance’s solubility, which is described as the highest achievable concentration of solute. The solubility rules assist in establishing whether the chemicals are soluble and, if yes, how much they are soluble.

Generally, three primary outcomes depend on a solute’s solubility: 

• A dilute solution contains less than the maximum amount of solute that it may dissolve.   
• A saturated solution contains approximately the same level of solute as its solubility.
• An extra saturated solution contains excess solutes, separating the extra solutes from the solution. If the separation process includes crystallization, a precipitate is formed. Precipitation reduces the concentration of a solute to saturation, increasing the solution’s solubility.

The rules for basic ionic solids are as follows. 

• Group I elements (Na+, Li+, K+, Rb+, Cs+) are all soluble in salts. This rule has a few exclusions. Ammonium ion-containing salts (NH₄+) are also soluble.
• Nitrate ion (NO₃-) salts are typically soluble.
• Salts comprising Br-, Cl -, or I – are soluble. The halide salts of Pb2+, Ag+, and (Hg2)2+ are notable exclusions to this norm. Hence, PbBr AgCl and Hg₂ Cl₂ are all insoluble.
• The majority of silver salts are insoluble. Examples of common silver soluble salts are Ag(C₂ H₃O₂ ) and AgNO₃; other than these two, all other silver salts are insoluble.
• The majority of sulphate salts are soluble. Some important outliers to solubility rules are BaSO₄ CaSO₄, PbSO₄, SrSO_4, and Ag2SO₄.
• The majority of hydroxide salts are just marginally soluble. Group, I elements’ hydrated salts are soluble. Group II elements (Sr, Ca, and Ba) are marginally soluble in their oxide salts. Transition metal and Al3+ hydrated salts are insoluble. As a result, Al(OH), Fe(OH), and Co(OH)2 are insoluble.
• Most transitional metal sulphides, particularly FeS, CdS, ZnS, and Ag2S, are insoluble. Sulphides of antimony, arsenic, lead, and bismuth are also insoluble.
• Carbonates are often insoluble. Group II carbonates (SrCO₃, CaCO_3, and BaCO₃) and PbCO3 and FeCO₃ are insoluble.
• Chromates are often insoluble. BaCrO₄ and PbCrO₄ are two common examples.
• Ag3PO4 and Ca3(PO4)2 are examples of insoluble phosphates.
• Similarly, fluorides like MgF₂, BaF_2, and PbF₂ are often insoluble.

Solubility Table

The role of the solubility table is to determine whether a material will dissolve or not in the solvent. When a material completely dissolves in water, it creates an aqueous solution designated in chemistry as (aq). If a solid material cannot dissolve in liquid, it remains solid, as indicated by the symbol (s) in chemistry.

The solubility table is divided into two columns. The left column highlights the list of all chemicals that can be dissolved in water, marked as soluble substances or (aq). The right column highlights the list of all chemical compounds that will not dissolve in liquid; these are marked as insoluble substances or (s).

The solubility table does not use the word “dissolve”. Thus, a common misunderstanding is that (s) stands for soluble while it stands for solid, an insoluble material that does not dissolve.

When an insoluble material combines with a solution, it forms a precipitate. So, if students are calculating a precipitation reaction, the right column contains a list of probable precipitates. 

Conclusion

Thus, solubility is the total amount of solute that may be dissolved in the solvent at a given temperature. A solution is a liquid that is a homogenous mixture of two or more solutes in a solvent. When a solute is combined and dissolved in water, that solute forms an aqueous solution.

Aqueous solutions are those solutions in which water is the solvent. Some solids or solutes are incompatible with the water or solvent. These are referred to as insoluble substances. 

Frequently Asked Questions

1. What is solubility definition chemistry? 

Ans. Solubility is the maximum amount of one matter that can be entirely dissolved or mixed with another. It defines the maximum amount of solute that can be mixed in a solvent at its equilibrium stage, resulting in the formation of a saturated solution.

When all additional requirements are fulfilled, more solute can be dissolved in the solvent beyond its equilibrium solubility point, forming a supersaturated solution. Adding extra solute after saturation or supersaturation does not enhance the solution concentration. Rather, the extra solute begins accumulating as a precipitate in the solution. 

2. What is the exsolution?

Ans. In mineralogy, exsolution is the process by which an originally homogeneous solid solution differentiates itself from two or more different crystalline minerals without adding or removing any other material. In most cases, it happens when the solution is cooled below the temperature of mutual stability or solubility.

Some examples of exsolutions are potassium-rich feldspar orthoclase (KAlSi3O8) and sodium-rich feldspar albite (NaAlSi3O8). They can exist in a homogeneous solid solution, although their exsolution can occur below a particular temperature.

3.Define solubility and miscibility.

Ans. If material is soluble in all amounts in a given solvent, it is said to be miscible. The term used for this property is called miscibility. Water and ethanol are two examples of miscible substances. They can dissolve as much quantity in themselves. On the contrary, oil and water neither mix nor dissolve. Thus water and oil are said to be immiscible.