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Laws of Thermodynamics:
a. First Law of Thermodynamics (Law of Energy Conservation):
ΔU = Q - Wb. Second Law of Thermodynamics:
ΔS ≥ Q/Tc. Third Law of Thermodynamics:
The entropy of a pure crystalline substance approaches zero as the temperature approaches absolute zero (0 K). -
Ideal Gas Laws:
a. Ideal Gas Law:
PV = nRTb. Boyle's Law:
PV = constant (for a fixed amount of gas at constant temperature)c. Charles's Law:
V/T = constant (for a fixed amount of gas at constant pressure)d. Avogadro's Law:
V/n = constant (for a fixed amount of gas at constant temperature and pressure) -
Enthalpy:
H = U + PV
where H is the enthalpy, U is the internal energy, P is the pressure, and V is the volume. -
Entropy:
ΔS = Q/T
where ΔS is the change in entropy, Q is the heat added to the system, and T is the temperature. -
Carnot Cycle:
The Carnot cycle is an idealized reversible thermodynamic cycle consisting of four processes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression. The efficiency of a Carnot engine is given by:
η = 1 - (Tc/Th)
where η is the efficiency, Tc is the absolute temperature of the cold reservoir, and Th is the absolute temperature of the hot reservoir. -
Clausius-Clapeyron Equation:
ln(P2/P1) = ΔHvap/R * (1/T1 - 1/T2)
This equation relates the vapor pressure of a substance to its enthalpy of vaporization and temperature. -
Gibbs Free Energy:
ΔG = ΔH - TΔS
where ΔG is the change in Gibbs free energy, ΔH is the change in enthalpy, T is the temperature, and ΔS is the change in entropy. -
Maxwell's Relations:
These are a set of relations derived from the fundamental equations of thermodynamics, allowing for the calculation of partial derivatives and the interrelation of thermodynamic properties. -
Stefan-Boltzmann Law:
The total power radiated by a black body is proportional to the fourth power of its absolute temperature:
P = σεAT^4
where P is the power, σ is the Stefan-Boltzmann constant, ε is the emissivity, A is the surface area, and T is the temperature. -
Heat Capacity:
The heat capacity of a system is the amount of heat required to raise its temperature by a certain amount. It is given by:
C = Q/ΔT
where C is the heat capacity, Q is the heat added to the system, and ΔT is the change in temperature. -
Specific Heat:
The specific heat of a substance is the amount of heat required to raise the temperature of a unit mass of the substance by a certain amount. It is given by:
c = Q/(mΔT)
where c is the specific heat, Q is the heat added to the substance, m is the mass of the substance, and ΔT is the change in temperature. -
Van der Waals Equation:
(P + a/V^2)(V - b) = RT
The Van der Waals equation is an improvement over the ideal gas law, accounting for the finite size of gas molecules (b) and intermolecular forces (a). -
Gibbs-Duhem Equation:
The Gibbs-Duhem equation relates the partial derivatives of intensive thermodynamic variables in a system. For a homogeneous system, it can be expressed as:
SdT - VdP + Ndm = 0
where S is the entropy, T is the temperature, V is the volume, P is the pressure, N is the number of moles, and m is the chemical potential. -
Joule-Thomson Effect:
The Joule-Thomson effect describes the change in temperature of a gas when it undergoes a throttling process. The temperature change (ΔT) is given by:
ΔT = μ/Cp * ΔP
where μ is the Joule-Thomson coefficient and Cp is the heat capacity at constant pressure. -
Raoult's Law:
Raoult's law relates the vapor pressure of an ideal solution to the vapor pressures of its components and their mole fractions. It is given by:
P = P₁x₁ + P₂x₂ + ... + P_nx_n
where P is the vapor pressure of the solution, P₁, P₂, ..., P_n are the vapor pressures of the components, and x₁, x₂, ..., x_n are their respective mole fractions. -
Antoine Equation:
The Antoine equation is used to calculate the vapor pressure of a pure substance as a function of temperature. It is expressed as:
log10(P) = A - (B / (T + C))
where P is the vapor pressure, T is the temperature in Celsius, and A, B, and C are constants specific to the substance. -
Nernst Equation:
The Nernst equation relates the cell potential of an electrochemical cell to the concentration and activity of the reactants and products. It is given by:
Ecell = E°cell - (RT/nF) * ln(Q)
where Ecell is the cell potential, E°cell is the standard cell potential, R is the gas constant, T is the temperature, n is the number of electrons transferred, F is Faraday's constant, and Q is the reaction quotient. -
Clapeyron Equation:
The Clapeyron equation relates the rate of change of saturation vapor pressure with temperature to the latent heat of vaporization. It is expressed as:
dp/dT = L/TΔV
where dp/dT is the derivative of vapor pressure with respect to temperature, L is the latent heat of vaporization, T is the temperature, and ΔV is the change in volume. -
Boltzmann's Entropy Formula: The entropy of a system can be calculated using Boltzmann's formula:
S = k * ln(W)
where S is the entropy, k is Boltzmann's constant, and W is the number of microstates corresponding to a given macrostate. -
Maxwell-Boltzmann Distribution:
The Maxwell-Boltzmann distribution describes the distribution of speeds of particles in a gas. It is given by:
f(v) = (4πv^2 / (2πkT/m)^(3/2)) * exp(-mv^2 / (2kT))
where f(v) is the probability density function, v is the velocity of the particle, T is the temperature, m is the mass of the particle, and k is Boltzmann's constant. -
Stefan-Boltzmann Law (Alternate Form):
The total power radiated by a black body per unit area is given by:
P/A = σT^4
where P/A is the power per unit area, σ is the Stefan-Boltzmann constant, and T is the temperature. -
Clapeyron-Mendeleev Equation:
The Clapeyron-Mendeleev equation relates the rate of change of vapor pressure with temperature for a liquid phase transition. It is expressed as:
d(ln P)/dT = ΔHvap / (RT^2)
where P is the vapor pressure, T is the temperature, ΔHvap is the enthalpy of vaporization, R is the gas constant. -
Gibbs-Helmholtz Equation:
The Gibbs-Helmholtz equation relates the change in Gibbs free energy (ΔG) with respect to temperature. It is given by:
ΔG = ΔH - TΔS
where ΔG is the change in Gibbs free energy, ΔH is the change in enthalpy, T is the temperature, and ΔS is the change in entropy. -
Kirchhoff's Law of Thermal Radiation:
Kirchhoff's law states that for an object in thermal equilibrium, the emissivity (ε) of a body is equal to its absorptivity (α) at a given wavelength and temperature:
ε = α -
Gibbs-Duhem Relation:
The Gibbs-Duhem relation is a mathematical relationship between the partial derivatives of intensive properties in a system. For a two-component system, it can be expressed as:
x1dμ1 + x2dμ2 = 0
where x1 and x2 are the mole fractions of the components, μ1 and μ2 are the chemical potentials of the components. -
Reciprocity Relations:
Reciprocity relations describe the symmetry of certain derivatives in thermodynamics. For example, the Maxwell relations can be derived from the reciprocity relations. -
Principle of Equipartition of Energy:
According to the principle of equipartition of energy, in thermal equilibrium, each quadratic term in the total energy of a system has an average value of (1/2)kT, where k is Boltzmann's constant and T is the temperature. -
Clasius-Mossotti Equation:
The Clasius-Mossotti equation relates the polarizability (α) of a substance to its dielectric constant (ε). It is given by:
α = (3ε₀ / 4π) * (ε - 1) / (ε + 2)
where ε₀ is the permittivity of free space.
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