Solutions: Molarity, Molality, Henry's & Raoult's Law

• Molarity (M) is the number of moles of solute per liter of solution and is temperature-dependent.
• Molality (m) is the number of moles of solute per kilogram of solvent and is temperature-independent.
• Mole fraction (x) is the ratio of moles of a component to the total moles of all components in a solution.

Henry's Law

• The partial pressure of a gas (p) in the vapor phase is proportional to its mole fraction (x) in the solution: P = KHx, where KH is Henry's law constant.

Applications of Henry’s Law

• Packing of soda/soft drinks
• Used in deep-sea diving
• Lung function
• Explains breathing problems at high altitudes due to low pressure, leading to Anoxia

Vapor Pressure

• The pressure exerted by a vapor over a liquid surface at equilibrium.

Raoult's Law

• The vapor pressure of any volatile component in a solution is directly proportional to its mole fraction.
• For solutions containing non-volatile solutes, vapor pressure (p) directly relates to the mole fraction of volatile solvent (xA): p = p°xA

Ideal Solutions

• Follow Raoult's law at varying temperatures and concentrations: P = PA + PB.
• Intermolecular forces are the same as in pure components: A-B = A-A = B-B
• No volume change upon mixing: ΔV mix = 0
• No heat change upon mixing: ΔH mix = 0
• Example: n-hexane + n-heptane & benzene + toluene.

Non-Ideal Solutions

• Do not follow Raoult's law at varying temperatures and concentrations: P ≠ PA + PB
• Intermolecular forces are different from those in pure components: A-B ≠ A-A, B-B
• Volume changes upon mixing: ΔV mix ≠ 0
• Heat changes during mixing: ΔH mix ≠ 0
• Example: Acetone + Water & Acetone + CHCl3.

Non-Ideal Solutions Showing Positive Deviation from Raoult's Law

• PT > PA + PB
• Intermolecular forces are weaker than pure components.
• Volume increases upon mixing: ΔV mix = +ve
• Endothermic mixing process: ΔH mix = +ve
• Examples: Acetone + Water, Alcohol + Water, Carboxylic Acid + Water.

Non-Ideal Solutions Showing Negative Deviation from Raoult's Law

• PT < PA + PB
• Intermolecular forces are stronger than pure components.
• Volume decreases upon mixing: ΔV mix = -ve
• Exothermic mixing process: ΔH mix = -ve
• Examples: Acetone + CHCl3, HNO3 + H2O

Azeotropes (Constant Boiling Mixtures)

• Solutions with a fixed composition that boil at a constant temperature irrespective of the boiling points of pure components.
• Minimum Boiling Azeotropes boil at a temperature lower than the boiling points of the pure components, example 95% Alcohol.
• Maximum Boiling Azeotropes boil at a temperature higher than the boiling points of the pure components; 68% HNO3.

Colligative Properties

• Properties of dilute solutions that depend only on the number of solute particles, not their identity.
• Relative Lowering of Vapor Pressure: (P1° - P1) / P1° = (W2 x M1) / (M2 x W1)
• Elevation of Boiling Point: ΔTb = Kb * m
• Depression of Freezing Point: ΔTf = Kf * m
• Osmotic Pressure: Π = CRT (C = Molarity)

Osmosis

• Movement of pure solvent from a region of lower concentration to a region of higher concentration through a semi-permeable membrane.
• Osmotic Pressure: Excess pressure needed to stop solvent flow through a semi-permeable membrane. Reverse Osmosis: Applying pressure greater than osmotic pressure reverses solvent flow from high to low concentration, used in water purification.
• Van't Hoff Factor (i) = Observed colligative property (actual)/ Theoretical colligative property (expected)

Electrochemistry: Conductance and Resistance

• Conductance (G) is the reciprocal of resistance (R): G = 1/R, measured in Siemens (Ω⁻¹).
• Specific Resistance (ρ) is measured in ohm-cm: ρ= RA/l
• Specific Conductance or Conductivity (κ) is the reciprocal of specific resistance: κ = 1/ρ

Molar Conductivity (Λm)

• Defined as the conducting power of all ions produced by one gram mole of an electrolyte in a solution, unit Scm²mol-1. Λᵐ = (κ × 1000) / Molarity

Variation of Molar Conductivity

• Strong electrolytes: Conductivity decreases slightly with increasing concentration.
• Weak electrolytes: Conductivity increases sharply with decreasing concentration as ionization increases upon dilution.

Kohlrausch's Law

• Molar conductivity of an electrolyte at infinite dilution is the sum of individual ion contributions eg. ^° CaCl2= ^°(Ca²+) +22 °(Cl⁻)

Applications of Kohlrausch's Law

• Calculating limiting molar conductivity: Ʌ°m = Ʌ°c + Ʌ°a
• Calculating degree of dissociation: α = Ʌ°m/Ʌ°m
• Calculating dissociation constant: Ka = Cα² / (1-α)

Faraday's Laws of Electrolysis

• First Law: Substance amount deposited during electrolysis is proportional to the quantity of electricity passed: w = Zit
• Second Law: Different substance amount liberated by same electricity quantity is proportional to their chemical equivalent weights: w1/w2 = E1/E2

Nernst Equation

• Ecell = E°cell - (0.059/n) log ([product]/[react.])
• Equilibrium constant Kc : Ecell = 0 log Kc = (n/0.059)E°cell

Electrochemical Cel and Gibbs energy of the reaction

• ΔrG° = -nFE°
• ΔrG° = -2.303RT log K

Products of Electrolysis

• NaCl Molten: Cathode: Na+ + e- → Na(s), Anode: Cl- → 1/2 Cl2 + e-
• NaCl Aq: Cathode: H2O + e- → 1/2 H2+ OH-, Anode: Cl - → 1/2 Cl2 + e-
• AgNO3 Aq-Ag electrodes: Cathode: Ag++ e → Ag(s), Anode: Ag(s) → Ag+ + e-

Electrochemical Cell

• Converts chemical energy to electrical energy.
• Based on spontaneous redox reactions.
• The Mercury Cell provides constant voltage, doesn't corrode.
• Dry Cell has a voltage of 1.5V; contains ZnCl2 to make complex
• Reactions in Lead Storage Batteries can be reversed to be Recharged

Electrolytic Cell

• Converts electrical energy into chemical energy through non-spontaneous reactions.

Unit-3: Electrochemistry Cell Types

• Fuel Cells can be eco-friendly with 60-70% efficiency.
• Corrosion is prevented through painting or using sacrificial metals like Mg/Zn.

Corrosion

• Corrosion by oxidation: Anode Fe(s) → Fe2+(aq) + 2e-
• Atmospheric oxidation 2Fe2+(aq) + 2H2O(l) + ½O2(g) → Fe2O3(s) +4H+(aq)

Chemical Kinetics: Rate of Reaction

• Defined as change in concentration of reactant or product per unit time.
• Rate = ± d[ ] /dt (mol L⁻¹ time⁻¹)
• Expressed as Rate Law: Rate = k[Reactant]ⁿ

Order of Reaction: Zero, First, and Second

• Zero: Rate = k
• First: Rate = k[A]
• Second: Rate = k[A]² or k[A][B]

Differential Rate Laws

• Express rate as function of concentration.

Integrated Rate Laws and Applications

• Zero Order: [A]t = -kt + [A]₀
• Rate constant unit: mol L⁻¹ s⁻¹
• First Order: ln[A]t = -kt + ln[A]₀ or k = (2.303/t)log([A]₀/[A]t)
• Units: s⁻¹

Half-Life concept

• time required to reduce reactant concentration to half the initial value, helpful in determining reaction rates:
• t1/2 = [A]₀/2k (zero order),
• t1/2 = 0.693/k (first order)

Arrhenius Equation

• Illustrates the relationship between activation energy, rate constant, and temperature
• k = Ae^(-Ea/RT)

Activation Energy

• Minimum extra energy to cause reaction.

Catalysis

• Homogeneous, heterogeneous, or enzyme
• Speeds up reaction by lowering activation energy.

Reaction Mechanism

• SN1: Two-step, forms carbocation intermediate.
• SN2: Single-step, concerted, inversion of stereochemistry.
• Acid Catalyzed Hydration of Alkenes: Follows carbocation pathway, Markanikov's product.

Polymers: Types, Structures, and Properties

• Addition versus condensation polymers
• Thermoplastics and thermosets
• Elastomers & fibers

Biomolecules: Carbohydrates

• Monosaccharides
• Oligosaccharides
• Polysaccharides

Lipids

• Fats and oils
• Phospholipids
• Steroids

Proteins: Classifications, Structure, and Functions

• Amino acids
• Primary, secondary, tertiary, and quaternary structures
• Denaturation

Nucleic Acids

• DNA and RNA: Structure, differences, and functions
• Genetic code

Hormones and Vitamins

• Types and functions

Haloalkanes, Haloarenes - Reactions and Mechanisms

• SN1, SN2, E1, E2, including stereochemistry Haloalkanes, Haloarenes- Uses and Environmental effects
• DDT and more

Alcohols, Phenols, and Ethers

• Acidic, Reactions and Applications

Aldehydes, Ketones, and Carboxylic Acids

• Reactions and Applications
• Wolff-Kishner Reduction
• Rosenmund Reduction
• Cannizzaro Reaction
• Clemmensen Reduction

Amines

• Reactions and Applications
• Gabriel Phthalimide
• Hoffman Bromamide

Coordination Compounds – Structures and Isomerism

• Werner’s Theory, VBT, CFT

Coordination number: Complex shape, Ligands

• Provide Pair of electrons for coordinate bond to central metal atom (Lewis Base)
• Monodentate, Bidentate, Ambidentate

Isomerism-

-Structural and Stereoisomerism: [geometrical, optical]

Organometallics, and Stability

• Preparation and properties

Metal Carbonyls - Nature of bonding

• Applications
• Biological System: Chlorophyll – complex of Mg.Hemoglobin – complex of Fe, Vit. B-12 – complex of Co