Short Answer

Solubility is the ability of a substance (solute) to dissolve in a solvent to form a homogeneous solution at a given temperature and pressure.

For example, sodium chloride dissolves in water, forming a salt solution. Solubility is important in chemistry, biology, and industry, as it determines how much of a substance can be dissolved, absorbed, or reacted in a liquid.

Detailed Explanation :

Definition of Solubility

Solubility is a measure of how much solute can dissolve in a solvent to produce a saturated solution. It depends on nature of solute and solvent, temperature, and pressure.

• A solute that dissolves easily is considered highly soluble.
• A solute that dissolves very little is considered sparingly soluble or insoluble.

1. Factors Affecting Solubility

1. Nature of Solute and Solvent
   • “Like dissolves like” principle:
     • Polar solutes dissolve in polar solvents (e.g., NaCl in water).
     • Non-polar solutes dissolve in non-polar solvents (e.g., iodine in carbon tetrachloride).
2. Temperature
   • For solid solutes, solubility generally increases with temperature.
   • For gases, solubility usually decreases with temperature.
     • Example: Carbon dioxide in water is less soluble at higher temperatures.
3. Pressure
   • Mainly affects gases dissolved in liquids.
   • Higher pressure increases gas solubility (Henry’s law).
     • Example: Soda is more fizzy under high pressure because CO₂ is more soluble.
4. Particle Size
   • Smaller particles dissolve faster due to increased surface area.

2. Types of Solubility

1. Complete Solubility
   • Solute dissolves completely in solvent.
   • Example: Sugar in water.
2. Partial or Limited Solubility
   • Only a small amount dissolves.
   • Example: Barium sulfate in water.
3. Insoluble Substances
   • Do not dissolve appreciably.
   • Example: Sand in water.

3. Saturated, Unsaturated, and Supersaturated Solutions

• Saturated Solution
  • Contains the maximum amount of solute that can dissolve at a given temperature.
• Unsaturated Solution
  • Contains less solute than maximum, more can dissolve.
• Supersaturated Solution
  • Contains more solute than the normal solubility; unstable.
  • Example: Sodium acetate solution prepared at high temperature then cooled.

4. Solubility in Everyday Life

1. Cooking
   • Salt and sugar dissolve in water to enhance taste.
2. Medicine
   • Drugs must be soluble in body fluids for absorption.
3. Industrial Applications
   • Solubility is important in chemical reactions, dyeing fabrics, and extraction processes.
4. Environmental Chemistry
   • Solubility affects pollutant distribution in water bodies.

5. Measurement of Solubility

• Solubility is expressed as grams of solute per 100 g of solvent or moles per liter.
• Example: 36 g of NaCl dissolves in 100 g of water at 25°C.
• Graphs called solubility curves show solubility changes with temperature.

6. Summary

• Solubility is the ability of a solute to dissolve in a solvent.
• Depends on nature of substances, temperature, and pressure.
• Types include complete, partial, and insoluble solubility.
• Vital in cooking, medicine, industry, and environmental studies.

Conclusion

Solubility is a fundamental concept in chemistry that determines how much of a substance can dissolve in a solvent. It is affected by temperature, pressure, and chemical nature of solute and solvent. Understanding solubility helps in preparing solutions, designing chemical processes, and practical applications in daily life, such as cooking, medicine, and industrial operations. Knowledge of solubility also guides pharmaceutical formulations and environmental safety measures.