Physical & Chemical Principles
"Future Chemical Engineer! Physical & Chemical Principles - the foundation of all chemical processes. Thermodynamics, kinetics, and transport phenomena!"
1. Thermodynamics ⚡
Energy transformations in chemical systems - the laws that govern all processes!
First Law (Conservation of Energy)
ΔU = Q - W
Energy cannot be created or destroyed. Change in internal energy = Heat added - Work done
For steady flow: ΔH + Δ(v²/2) + gΔz = Q - Ws
Second Law (Entropy)
ΔS_universe ≥ 0
Entropy of an isolated system always increases. Heat flows from hot to cold spontaneously.
Carnot efficiency: η = 1 - Tc/Th (maximum theoretical efficiency)
Gibbs Free Energy
ΔG = ΔH - TΔS
Predicts spontaneity: ΔG < 0 = spontaneous, ΔG > 0 = non-spontaneous
At equilibrium: ΔG = 0, K = exp(-ΔG°/RT)
2. Chemical Equilibrium ⚖️
| Concept | Equation | Application |
|---|---|---|
| Equilibrium Constant | K = [Products]/[Reactants] | Predicts reaction extent |
| Le Chatelier's Principle | System opposes change | Optimize reactor conditions |
| van't Hoff Equation | d(lnK)/dT = ΔH°/RT² | Temperature effect on K |
| Phase Rule | F = C - P + 2 | Degrees of freedom |
3. Chemical Kinetics 🚀
Reaction Orders
- Zero order: [A] = [A]₀ - kt
- First order: ln[A] = ln[A]₀ - kt
- Second order: 1/[A] = 1/[A]₀ + kt
Half-life (1st order): t½ = ln2/k = 0.693/k
Arrhenius Equation
k = A·e^(-Ea/RT)
- A = pre-exponential factor
- Ea = activation energy
- Higher T → faster reaction
4. Physical Chemistry Fundamentals 🔬
Ideal Gas Law
PV = nRT
R = 8.314 J/mol·K = 0.0821 L·atm/mol·K
Real Gases (van der Waals)
(P + a/V²)(V - b) = RT
a = molecular attraction, b = molecular volume
Raoult's Law
Pᵢ = xᵢPᵢ°
Partial pressure = mole fraction × vapor pressure (ideal solutions)
5. Electrochemistry ⚡
Key Equations
Nernst Equation:
E = E° - (RT/nF)ln(Q)
At 25°C: E = E° - (0.0592/n)log(Q)
Faraday's Laws:
m = (M × I × t)/(n × F)
F = 96,485 C/mol
6. Practice Questions 📚
Common Board Exam Questions
Q1: Calculate the equilibrium constant K if ΔG° = -10 kJ/mol at 298K.
A: K = exp(-ΔG°/RT) = exp(10000/(8.314×298)) = exp(4.04) = 56.8
Q2: A first-order reaction has k = 0.01 s⁻¹. What is the half-life?
A: t½ = ln(2)/k = 0.693/0.01 = 69.3 seconds
Q3: What is the maximum efficiency of a heat engine operating between 500K and 300K?
A: η = 1 - Tc/Th = 1 - 300/500 = 1 - 0.6 = 0.4 = 40%
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