Solubility

Solubility is a fundamental concept in chemistry that describes the ability of a substance to dissolve in a particular solvent under specific conditions to form a solution. A fluid may or may not dissolve completely in a fluid. Understanding the concept of solubility is essential in many fields of science, including pharmaceuticals, environmental science, and materials science.

In this article, we will explore the key concepts of solubility, such as factors that affect solubility, solubility product, and solubility of different phases of matter with each other.

What is Solubility?

Solubility of any solvent is the maximum amount of the solute that can be dissolved in any solvent at any certain temperature. Suppose if we dissolve sugar in the water then the amount of sugar that can be dissolved in water at any given temperature defines the solubility of sugar in water.

Solubility Definition

Solubility refers to the greatest amount of solute that can dissolve in a known quantity of solvent at a given temperature.

In a solvent, a solution is a homogeneous mixture of one or more solutes. A common example of a solution is sugar cubes added to a cup of tea or coffee. Solubility is the property that allows sugar molecules to dissolve. As a result, solubility can be defined as the ability of a material (solute) to dissolve in a specific solvent. Any substance dissolved in a solvent, whether solid, liquid, or gas, is referred to as a solute.

Solubility Effects on Reactions

If we dissolve any solute in a solvent then there are three possible result that are,

Dilute Solution: If a solvent has less solute dissolve in forming the solution then this solution is called the Dilute Solution.

Saturated Solution: If a solvent has maximum solute(that can be dissolved without changing the temperature) dissolve in forming the solution then this solution is called the Saturated Solution.

Precipitate Solution: If a solvent we add excess solute then its saturation limit then it forms the solution in which precipitate is formed also called precipitate solution.

Solubility Product

“Solubility product” refers to salts that are only sparingly soluble. It is the maximal product of the molar concentration of the ions produced by the dissociation of the molecule (raised to their proper powers).

The solubility product remains constant at a given temperature. The lower the value of the solubility product, the lower the solubility, and the higher the value of the solubility product, the greater the solubility. The elements that influence solubility vary depending on the condition of the solute:

• Solubility of Liquids In Liquids
• Solubility of Solids In Liquids
• Solubility of Gases In Liquids

Now let’s learn about the same in detail.

Solubility of Liquids In Liquids 

Water is referred to as a universal solvent since it dissolves practically all solutes, with the exception of a few. A substance’s solubility can be influenced by a number of circumstances.

Solubility refers to the development of a new bond between the solute and solvent molecules. Solubility is the highest concentration of solute that dissolves in a known concentration of solvent at a particular temperature in terms of quantity. Solutes are classified as highly soluble, sparingly soluble, or insoluble based on the concentration at which they dissolve in a solvent. It is stated to be soluble if a concentration of 0.1 g or more of a solute can be dissolved in a 100 ml solvent. It is considered to be sparingly soluble when a concentration of less than 0.1 g is dissolved in the solvent. As a result, solubility is defined as a quantitative expression measured in grams per liter (g/L).

Different sorts of solutions can be obtained based on solubility. At a given temperature, a saturated solution is one in which a given amount of solute is entirely soluble in a solvent. A supersaturated solution, on the other hand, is one in which the solute begins to salt out or precipitate once a specific concentration is dissolved at the same temperature.

Factors Affecting Solubility of Liquid in Liquid

The factors affecting the Solubility of Liquid in Liquid are discussed below,

Effect of Pressure

Pressure has a significantly greater impact on gases than it does on solids and liquids. When a gas’s partial pressure rises, so does the likelihood of its solubility. CO₂ is bottled under high pressure in a soda bottle, for example.

Effect of Temperature

 People can boost a solute’s solubility characteristic by adjusting the temperature. At 20° C or 100° C, water generally dissolves solutes. Increased temperature will totally dissolve sparingly soluble solid or liquid compounds. However, in the case of a gaseous substance, temperature affects solubility in the opposite direction, meaning that as the temperature rises, gases expand and escape from their solvent.

Solubility of Solids In Liquids 

Solid solubility has been observed to be dependent on both the composition of the solute and the solvent. People frequently see that some substances, such as sugar and common salt (NaCl), dissolve quickly in water whereas others, such as naphthalene, do not. Only polar solutes prefer to dissolve in polar solvents, while non-polar solvents dissolve only in non-polar solutes, according to different observations and experimental data. As a result, one of the most important elements impacting solubility is the composition of the solvent. The discovery that like dissolves like led to the conclusion that polar solvents dissolve polar solutes and non-polar solvents dissolve non-polar solutes.

Let’s take a closer look at how a solid dissolves in a solvent. Dissolution occurs when a solid solute is given to a solvent and the solute particles dissolve in the solvent. The process of crystallization occurs when solute particles in a solution clash with one another and some of the particles separate from the solution.

Between these two processes, a state of dynamic equilibrium is formed, at which point the number of solute molecules entering the solution equals the number of particles exiting the solution. As a result, at a given temperature and pressure, the concentration of the solute in the solution will remain constant.

A saturated solution is one in which no more solute can dissolve in the solvent at a given temperature and pressure, and it contains the maximum amount of solute. Solubility refers to the concentration of a solute in a solution at a certain temperature and pressure. An unsaturated solution is one in which more solute can be added to the solution.

Factors Affecting Solubility of Solids In Liquids

The factors affecting the Solubility of Solids in Liquid are discussed below,

Effect of Temperature

If (∆_solH > 0), the solubility of a nearly saturated solution increases as the temperature rises, and if (∆_solH < 0), the solubility falls as the temperature rises.

Nature Solute and Solvent

Like disintegrates into like. Anthracene, for example, does not react with sodium chloride. Naphthalene and anthracene, on the other hand, dissolve quickly in benzene, whereas sodium chloride and sugar do not.

Effect of Pressure

 Changes in pressure have little effect on solid solubility. This is owing to the fact that solids and liquids are highly incompressible and are essentially unaffected by pressure fluctuations.

Solubility of Gases In Liquids 

The topic of gas solubility in liquids is concerned with the idea of gas dissolving in a solvent. Let’s start with a definition of solubility. Solubility is the greatest amount of solute that may be dissolved in a given solvent at a given temperature for any substance. Our current interest is the solubility of gases in liquids. The gas solubility in liquids is greatly affected by temperature and pressure as well as the nature of the solute and the solvent.

Many gases dissolve quickly in water, while others do not under typical conditions. Oxygen is only slightly soluble in water, whereas HCl or ammonia dissolves quickly.

Factors Affecting Solubility of Gases In Liquids

The factors affecting the Solubility of gas in Liquid are discussed below,

Effect of Pressure

It has been discovered that as pressure rises, so does the solubility of a gas in liquids. Consider a system of a gas solution in a solvent in a closed container in a state of dynamic equilibrium to better understand the effect of pressure on gas solubility. Because the solution is now in equilibrium, the rate of gaseous molecules entering it is equal to the rate of gaseous molecules leaving it. As a result, the number of gas molecules in the solution increases until a new equilibrium point is reached. As a result, the solubility of gases increases as the pressure of a gas above the solution rises.

Effect of Temperature

With increasing temperature, gas solubility in liquids decreases. Dissolution is the process by which gas molecules in a liquid dissolve. Heat is emitted throughout the process. When a system’s equilibrium is disturbed, the system readjusts itself in such a way that the effect that caused the change in equilibrium is offset, according to Le Chatelier’s Principle. Because dissolution is an exothermic process, solubility should decrease as the temperature rises, proving Le Chatelier’s Principle.

Learn more about, Factors affecting Solubility

Henry’s Law

According to Henry’s Law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas at a fixed temperature. More formally, “The partial pressure of the gas in the vapor phase (p) is proportional to the mole fraction of the gas (x) in the solution,” says the most popular version of Henry’s law. Mathematically it is given as:

p = K_Hx

Here, K_H is Henry’s Law constant

Applications of Henry’s Law

Henry’s Law is one of the most important laws used in solutions and its various applications are,

• In the manufacture of carbonated drinks.
• Climbers and those who live at high altitudes will benefit from Henry’s Law
• During a deep-water dive a diver uses Henry’s Law to use proper oxygen.

Raoult’s Law (Special Case of Henry’s Law)

According to Raoult’s law, “solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid”. Mathematically it can be written as

p = x_ip_i⁰

One of the components of a gas in a liquid solution is so volatile that it exists as a gas. According to Henry’s law, it is soluble in water.

p = K_Hx

As a result, Raoult’s law is a specific case of Henry’s law, in which K_H equals p_i⁰be dissolved

Read More,

• Vapour Pressure
• Solubility Equilibria
• Types of Solutions

Examples on Solubility

Example 1: At 313 K, benzene and toluene form perfect solutions A and B. 4 moles of toluene and 1 mole of C₆H₆ makeup Solution A. Toluene and benzene are equal amounts in Solution B. In each scenario, calculate the total pressure. At 313 K, C₆H₆ and toluene have vapor pressures of 160 and 60 mm, respectively.

Solution:

• For Solution A

P_M = P^‘_B + P^‘_T = (P⁰_B × X_B) + (P⁰_T × X_T)

P_M = 160 × (1/1+4) + 60 × (4/1+4)

P_M = 32 + 48

P_M = 80 mm

• For Solution B

P_M = 160 × (92/170) + 60 × (78/170)

P_M = 86.588 + 27.529

P_M = 114.117 mm

Example 2: Heptane and octane form an ideal solution at 373 K, the vapor pressures of the pure liquids at this temperature are 105.2 kPa and 46.8 kPa respectively. If the solution contains 25g of heptane and 28.5g of octane, calculate the vapor pressure exerted by heptane.

Solution:

Given,

• P^o(C₇H₁₆) = 105.2 kPa
• P^o(C₈H₁₈) = 46.8 kPa
• M(C₇H₁₆) = 100g mol^-1
• M(C₈H₁₈) = 114g mol^-1

X{C₇H₁₆} = n(C₇H₁₆) / {n(C₇H₁₆) + n(C₈H₁₈)}

X{C₇H₁₆} = (25/100) / ((25/100) + (28.5/114))

X{C₇H₁₆} = 0.25/0.25 + 0.25

X{C₇H₁₆} = 0.5

X{C₈H₁₈} = 1 – 0.5 = 0.5

P{C₇H₁₆} = 105.2 × 0.5 = 52.60 kPa

FAQs on Solubility

1. What is Solubility in Chemistry?

Solubility is the ability of a substance (solute) to dissolve in a solvent to form a homogenous solution.

2. What Factors Affect Solubility?

The factor that affect the solubility are, Temperature, Pressure, and Chemical Nature.

3. How does Temperature Affect Solubility?

Solubility of solids in liquids increases with temperature, while the solubility of gases in liquids decreases with temperature.

4. How does Pressure Affect Solubility?

Solubility of gases in liquids increases with pressure, while the solubility of solids in liquids is generally unaffected by pressure.

5. What is Solubility Product Constant?

Solubility product constant (K_sp) is a measure of the maximum amount of a solute that can dissolve in a given solvent at a particular temperature and pressure.

6. What is the Difference between an Unsaturated, Saturated, and Supersaturated Solution?

 An unsaturated solution is a solution that contains less than the maximum amount of solute that can dissolve in a solvent. A saturated solution is a solution that contains the maximum amount of solute that can dissolve in a solvent. A supersaturated solution is a solution that contains more solute than is normally possible at a given temperature and pressure.

7. What is “Like Dissolves Like”?

This means that substances with similar polarities or intermolecular forces are more likely to dissolve in each other.

8. What are Effects of Temperature and Pressure on Solubility?

An increase in pressure and temperature contributes to higher solubility in this process. An rise in pressure causes more gas particles to enter the liquid, lowering the partial pressure. As a result, the solubility will rise.

9. What is Solubility Product Constant?

Solubility Constant denoted by Ksp is the equilibrium constant that represents the extent to which a solid solute dissolves in a solution.