Antoine Equation Vapor Pressure Calculator
Our physical chemistry calculator computes antoine equation vapor pressure accurately. Enter measurements for results with formulas and error analysis.
Calculator
Adjust values & calculateFormula
P is the vapor pressure (typically in mmHg), T is the temperature (typically in degrees Celsius), and A, B, C are substance-specific empirical constants. The equation accurately describes the exponential relationship between vapor pressure and temperature over moderate ranges.
Last reviewed: December 2025
Worked Examples
Example 1: Water at 100 C
Example 2: Ethanol at 78 C
Background & Theory
The Antoine Equation Vapor Pressure Calculator applies the following established principles and formulas. Chemistry is the science of matter's composition, structure, properties, and transformations. At the heart of quantitative chemistry lies the mole concept. One mole of any substance contains exactly 6.022×10²³ entities (Avogadro's number, Nₐ), and the molar mass of an element or compound in grams per mole is numerically equal to its atomic or molecular mass in atomic mass units. This allows chemists to convert between measurable mass and the number of reacting particles. Stoichiometry uses balanced chemical equations to relate the amounts of reactants and products. A balanced equation conserves both mass and charge. Molarity, the most common concentration unit, is defined as M = n/V, where n is moles of solute and V is volume of solution in liters, giving units of mol/L. Acidity and basicity are quantified by the pH scale, defined as pH = −log₁₀[H⁺], where [H⁺] is the molar concentration of hydrogen ions. Pure water at 25°C has pH 7.00; acids have lower values and bases higher values. Each unit change represents a tenfold change in hydrogen ion concentration. Gas behavior is described by the ideal gas law PV = nRT, where P is pressure in pascals, V is volume in cubic meters, n is moles, R = 8.314 J/(mol·K), and T is temperature in kelvin. Special cases include Boyle's Law (P₁V₁ = P₂V₂ at constant temperature) and Charles's Law (V₁/T₁ = V₂/T₂ at constant pressure). Thermochemistry quantifies heat changes in reactions through enthalpy, H. Hess's Law states that the total enthalpy change for a reaction is the sum of enthalpy changes for any sequence of steps leading to the same overall reaction, making it possible to calculate enthalpies for reactions that cannot be measured directly. Electron configuration describes the distribution of electrons in atomic orbitals according to the Aufbau principle, Pauli exclusion principle, and Hund's rule. Periodic trends including atomic radius, ionization energy, and electronegativity arise systematically from electron configuration and nuclear charge, enabling chemists to predict and rationalize chemical behavior across the periodic table.
History
The history behind the Antoine Equation Vapor Pressure Calculator traces back through the following developments. Chemistry's roots lie in alchemy, the medieval practice combining proto-scientific experimentation with mystical aims. Alchemists developed practical techniques including distillation, calcination, and the preparation of acids, building a body of empirical knowledge despite their theoretical misunderstandings. Modern chemistry is conventionally dated to Antoine Lavoisier (1743–1794), often called the father of modern chemistry. Lavoisier demonstrated the law of conservation of mass in 1789, showing that matter is neither created nor destroyed in chemical reactions. He identified oxygen's role in combustion, dismantling the phlogiston theory, and co-authored the first systematic chemical nomenclature, establishing the language still used today. John Dalton proposed the first modern atomic theory in 1803, asserting that all matter is composed of indivisible atoms, that atoms of the same element are identical in mass, and that compounds form from fixed ratios of different atoms. This provided a physical basis for Lavoisier's conservation law and Proust's law of definite proportions. Dmitri Mendeleev published his periodic table in 1869, arranging the 63 known elements by atomic mass and revealing repeating patterns of chemical behavior. He boldly left gaps for undiscovered elements and predicted their properties with remarkable accuracy, predictions confirmed by the subsequent discovery of gallium, scandium, and germanium. Ernest Rutherford's gold foil experiment in 1911 revealed the nuclear model of the atom: a tiny, dense, positively charged nucleus surrounded by electrons. Niels Bohr refined this in 1913 with a quantized model of electron orbits that explained the hydrogen emission spectrum. Quantum chemistry and molecular orbital theory, developed through the 1920s and 1930s, provided the full quantum mechanical description of chemical bonding. The latter 20th century saw the rise of computational chemistry, enabling molecular simulation at unprecedented scale. The green chemistry movement, articulated in the 12 Principles of Green Chemistry in 1998, reoriented the field toward sustainability, waste reduction, and benign chemical design, reflecting chemistry's growing awareness of its environmental responsibilities.
Frequently Asked Questions
Formula
log10(P) = A - B / (C + T)
P is the vapor pressure (typically in mmHg), T is the temperature (typically in degrees Celsius), and A, B, C are substance-specific empirical constants. The equation accurately describes the exponential relationship between vapor pressure and temperature over moderate ranges.
Worked Examples
Example 1: Water at 100 C
Problem: Calculate the vapor pressure of water at 100 C using Antoine constants A=8.07131, B=1730.63, C=233.426.
Solution: log10(P) = 8.07131 - 1730.63 / (233.426 + 100)\nlog10(P) = 8.07131 - 1730.63 / 333.426\nlog10(P) = 8.07131 - 5.18982\nlog10(P) = 2.88149\nP = 10^2.88149 = 760.96 mmHg
Result: P = 760.96 mmHg (approximately 1 atm, confirming boiling point)
Example 2: Ethanol at 78 C
Problem: Calculate ethanol vapor pressure at 78 C using A=8.20417, B=1642.89, C=230.300.
Solution: log10(P) = 8.20417 - 1642.89 / (230.300 + 78)\nlog10(P) = 8.20417 - 1642.89 / 308.300\nlog10(P) = 8.20417 - 5.32821\nlog10(P) = 2.87596\nP = 10^2.87596 = 751.22 mmHg
Result: P = 751.22 mmHg (near 760, confirming ~78 C boiling point)
Frequently Asked Questions
What is the Antoine equation?
The Antoine equation is a semi-empirical correlation that describes the relationship between vapor pressure and temperature for pure substances. The equation is log10(P) = A - B / (C + T), where P is the vapor pressure, T is the temperature, and A, B, and C are substance-specific constants determined from experimental data. It is one of the most widely used equations in chemical engineering for vapor pressure estimation due to its simplicity and reasonable accuracy over moderate temperature ranges. The equation was developed by French chemist Louis Charles Antoine in 1888.
What are Antoine constants and where do I find them?
Antoine constants (A, B, and C) are empirically determined parameters that are unique to each chemical substance and depend on the temperature range and pressure units used. They are tabulated in reference databases such as the NIST WebBook, the Yaws Handbook of Vapor Pressure, Perrys Chemical Engineers Handbook, and the DIPPR database. It is crucial to use constants that match your pressure units (typically mmHg or bar) and that are valid for your temperature range, as using constants outside their valid range can produce large errors in the calculated vapor pressure.
How accurate is the Antoine equation?
The Antoine equation is generally accurate to within 1-3% over its valid temperature range, which typically spans from about 10 C below the normal boiling point to the critical temperature. Its accuracy decreases significantly near the critical point and at very low temperatures far from the boiling point. For more accurate results over wider temperature ranges, extended Antoine equations with additional parameters or the Wagner equation are preferred. The three-parameter Antoine equation is favored in practice because it offers a good balance between accuracy and simplicity for engineering calculations.
What is vapor pressure and why does it matter?
Vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its liquid phase at a given temperature. It increases exponentially with temperature because more molecules have sufficient kinetic energy to escape the liquid surface. Vapor pressure is fundamental to many applications: it determines boiling points (a liquid boils when its vapor pressure equals atmospheric pressure), governs evaporation rates, is essential for designing distillation columns and evaporators, and is used in environmental science to predict volatility and atmospheric transport of chemicals.
How does the Antoine equation relate to the Clausius-Clapeyron equation?
The Clausius-Clapeyron equation provides the theoretical basis for the temperature dependence of vapor pressure: dln(P)/dT = delta_Hvap / (R * T^2), where delta_Hvap is the enthalpy of vaporization. Integrating this equation with the assumption of constant enthalpy gives ln(P) = -delta_Hvap/(RT) + constant, which is a two-parameter equation. The Antoine equation can be viewed as an improved empirical version that adds the C parameter to better fit experimental data, effectively accounting for the temperature dependence of delta_Hvap. When C = 0, the Antoine equation reduces to the Clausius-Clapeyron form.
Can I use Antoine Equation Vapor Pressure Calculator on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy