Summary of SOLUTIONS in One Shot: All Concepts & PYQs Covered | JEE Main & Advanced

Main Ideas and Concepts Covered

The chapter "Solutions" is a fundamental and relatively easy topic in Physical Chemistry, important for both 12th-grade and JEE aspirants.
It has consistent weightage in exams like JEE Main and Advanced.
Emphasis on revising all important chapters and practicing questions regularly.
Importance of practicing Previous Year Questions (PYQs) as they are highly predictive of exam patterns and difficulty level.

Definition: A solution is a homogeneous mixture of solute and solvent.
The phase of the solvent determines the phase of the solution.
If solute and solvent are in the same phase, the component in lesser quantity is solute, and the one in greater quantity is solvent.

Vapor pressure is the pressure exerted by vapor in equilibrium with its liquid at a given temperature.
Initially, evaporation rate is high (no vapor above surface), condensation rate zero.
Over time, evaporation and condensation rates become equal, establishing equilibrium.
Vapor pressure depends only on temperature (not on volume, amount of liquid, or container shape).
Vapor pressure increases with temperature due to increased kinetic energy of molecules (explained via kinetic energy distribution curve).
The relation between vapor pressure and temperature is exponential, not linear.
Formula relating vapor pressures at two temperatures using enthalpy of vaporization (ΔH_vap) and equilibrium constants (Kp).

Non-volatile solute in volatile solvent: Vapor pressure of solution decreases compared to pure solvent because solute particles reduce the number of solvent molecules escaping into vapor.
Raoult’s law: Vapor pressure of a component in solution = mole fraction of that component × vapor pressure of pure component.
For Solutions with volatile solutes and solvents, total vapor pressure = sum of partial pressures of each volatile component (each calculated using Raoult’s law).
Raoult’s law applies ideally when the solution behaves ideally (intermolecular interactions between components are similar).

Ideal Solutions: Intermolecular interactions between unlike molecules are similar to those between like molecules (ΔH_mix = 0, ΔV_mix = 0).
Non-ideal Solutions: Deviations occur due to differences in intermolecular forces.
- Positive Deviation: When interactions between unlike molecules are weaker than like molecules; vapor pressure is higher than predicted by Raoult’s law.
- Negative Deviation: When interactions between unlike molecules are stronger; vapor pressure is lower than predicted.
Examples:
- Positive deviation: Ethanol + cyclohexane, Ethanol + acetone, benzene + carbon tetrachloride.
- Negative deviation: Acetone + chloroform, benzene + chloroform (due to specific interactions like hydrogen bonding or π-complex formation).
Explanation of deviations based on molecular interactions: hydrogen bonding, dipole-dipole, Van der Waals (London dispersion) forces.

Miscible liquids mix completely; Raoult’s law applies.
Immiscible liquids do not mix; vapor pressure is sum of vapor pressures of each component, acting independently.
In immiscible systems, vapor phase composition and mole ratios can be calculated using vapor pressures of pure components.
Agitation can cause mixing and affect vapor pressure behavior.

Dalton’s law: Mole fraction of a component in vapor phase = partial pressure of that component / total vapor pressure.
Vapor phase composition can be calculated using Raoult’s law for partial pressures and Dalton’s law for mole fractions.
Formulas provided for calculating mole fractions in vapor and liquid phases.

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