Solubility, concentration terms: molarity, molality, normality

1. What are Solutions?

1. A solution is a homogeneous mixture of two or more substances.
2. The substance in larger quantity is called the solvent, and the one in smaller quantity is called the solute.
3. Solutions can exist in all three states: solid, liquid, and gas.

2. Types of Solutions

1. Solid in solid: Example: Alloys like brass (zinc in copper).
2. Solid in liquid: Example: Sugar dissolved in water.
3. Liquid in liquid: Example: Alcohol in water.
4. Gas in liquid: Example: Carbon dioxide in soda water.
5. Gas in gas: Example: Air (oxygen in nitrogen).

3. Solubility

1. Solubility is the maximum amount of solute that can dissolve in a solvent at a given temperature and pressure.
2. Factors affecting solubility include temperature, pressure, and the nature of solute and solvent.
3. For most solids, solubility increases with temperature, while for gases, solubility decreases with an increase in temperature.
4. Henry’s law: The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.

4. Concentration Terms

a. Molarity (M)

1. Molarity is the number of moles of solute dissolved in one liter of solution.
2. Formula: M = moles of solute / volume of solution (in liters).
3. Molarity changes with temperature as it depends on the volume of the solution.

b. Molality (m)

1. Molality is the number of moles of solute dissolved in 1 kilogram of solvent.
2. Formula: m = moles of solute / mass of solvent (in kg).
3. Molality is temperature-independent as it depends only on the mass of the solvent.

c. Normality (N)

1. Normality is the number of gram equivalents of solute dissolved in one liter of solution.
2. Formula: N = equivalents of solute / volume of solution (in liters).
3. Normality is often used in acid-base reactions and redox reactions.

5. Applications of Concentration Terms

1. Molarity is widely used in laboratory solutions and reactions.
2. Molality is useful in colligative property calculations as it is unaffected by temperature.
3. Normality is significant in titrations and equivalent-based calculations.

6. Key Points

1. A solution is a homogeneous mixture of solute and solvent.
2. Solubility depends on temperature, pressure, and the nature of substances.
3. Henry’s law explains gas solubility in liquids.
4. Molarity is temperature-dependent, while molality is temperature-independent.
5. Normality is widely used in acid-base and redox reactions.
6. Understand the formulas for M, m, and N to solve numerical problems efficiently.