This chapter introduces thermodynamics, the study of energy changes in chemical reactions and processes. Understanding thermodynamics is essential for predicting how and why reactions occur.
Thermodynamics – Formula & Equation Sheet
Essential formulas and equations from Chemistry Part - I, tailored for Class 11 in Chemistry.
This one-pager compiles key formulas and equations from the Thermodynamics chapter of Chemistry Part - I. Ideal for exam prep, quick reference, and solving time-bound numerical problems accurately.
Key concepts & formulas
Essential formulas, key terms, and important concepts for quick reference and revision.
Formulas
∆U = q + w
∆U is the change in internal energy, q is the heat added to the system, and w is the work done on the system. This equation expresses the first law of thermodynamics, stating energy conservation.
q = C × ∆T
q is the heat transferred, C is the heat capacity, and ∆T is the change in temperature. This formula calculates the heat absorbed or released when the temperature of a substance changes.
∆H = ∆U + ∆n_g RT
∆H is the change in enthalpy, ∆U is the change in internal energy, ∆n_g is the change in moles of gas, R is the universal gas constant, and T is the temperature in Kelvin. This relates enthalpy change to changes in states involving gases.
q_p = ∆H
q_p is the heat at constant pressure, which equals the change in enthalpy (∆H). This is useful for reactions occurring at a constant atmospheric pressure.
w = - p_ex ∆V
w is the work done on or by the system, p_ex is the external pressure, and ∆V is the change in volume. This equation calculates work in expansion (or compression) processes.
∆S = q_rev / T
∆S is the change in entropy, q_rev is the reversible heat transfer, and T is the temperature in Kelvin. This formula defines how the entropy of a system changes with heat transfer at a constant temperature.
∆S_total = ∆S_system + ∆S_surroundings
This equation expresses the second law of thermodynamics, stating that the total change in entropy (∆S_total) is the sum of changes in entropy of the system and its surroundings.
G = H - TS
G is the Gibbs free energy, H is the enthalpy, T is the temperature in Kelvin, and S is the entropy. This equation is central to determining spontaneity in chemical processes.
∆G = ∆H - T∆S
∆G is the change in Gibbs free energy, ∆H is the enthalpy change, and ∆S is the entropy change. This relationship allows us to evaluate the spontaneity of a reaction.
∆G = -RT ln K
Where K is the equilibrium constant. This equation relates the standard Gibbs free energy change to the equilibrium constant of a reaction at a given temperature.
Equations
PV = nRT
This is the ideal gas law, where P is pressure, V is volume, n is the number of moles of gas, R is the ideal gas constant, and T is temperature in Kelvin. It relates the state of an ideal gas.
H = U + PV
This defines enthalpy (H) as the sum of internal energy (U) and the product of pressure (P) and volume (V). It is essential for understanding enthalpy in reactions.
∆H = ΣH_products - ΣH_reactants
This is Hess's law for adding enthalpy changes in reactions. It states that the enthalpy change for a reaction is the sum of the enthalpy changes for each step.
q = n∆H_f
Where q is the heat absorbed/released, n is the number of moles, and ∆H_f is the heat of formation. This applies in calculating heat during formation reactions.
p∆V = ∆n_g RT
This equation relates the pressure and volume change (∆V) to the change in number of moles of gas (∆n_g), useful in gas expansion/compression calculations.
K = e^(-∆G/RT)
The relationship between the equilibrium constant (K), Gibbs free energy change (∆G), the gas constant (R), and temperature (T). It indicates how free energy relates to equilibrium position.
∆U = q + w
This is the first law of thermodynamics restated, where ∆U is the change in internal energy. Typically used for closed systems to understand energy transfers.
q = m×c×∆T
Where m = mass, c = specific heat capacity, and ∆T = temperature change. This formula calculates heat transfer in a specific heat scenario.
∆H = ∆U + ∆nRT
Expresses the enthalpy change of a system as a function of the internal energy change plus the product of number of moles of gas change, the temperature, and the gas constant.
∆S = k*ln(Ω)
Where k is Boltzmann's constant and Ω represents the number of microscopic configurations that correspond to a macroscopic state. It connects statistical mechanics with thermodynamics.
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