Vapor phase composition calculator

Raoult inputs: liquid mole fractions and pure vapor pressures

Model a two-component ideal liquid as open system equilibrium where each component contributes a partial pressure equal to its liquid mole fraction times its pure vapor pressure at the system temperature. Liquid fractions that sum above one fail validation because a binary basis cannot exceed a full mole. The engine does not look up Antoine constants or convert units: you supply P_i^sat already evaluated at the temperature of interest. Send x1 and x2 as finite numbers in the closed interval from zero to one; optional aliases mole_fraction_1, liquid_mole_fraction_1, and x_1 map to the first component, with the parallel aliases for component two. Pure vapor pressures p1_sat and p2_sat must be non-negative finite numbers in any coherent pressure unit—kilopascals, bars, atmospheres, or torr—as long as both pressures share that unit so the total pressure and the vapor fractions stay dimensionless and consistent. Numeric strings are accepted and coerced the same way as JSON numbers. Values outside zero to one, missing fields, non-finite magnitudes, and negative pure pressures all raise invalid_input and are not charged. Identical inputs always produce identical JSON because the path is pure arithmetic with no network, no random seed, and no wall clock, which makes the vapor phase composition calculator safe to pin in automated tests and classroom oracles.

Reading y1, y2, partial pressures, and the total pressure

On success the response echoes x1, x2, p1_sat, and p2_sat after stable rounding, then reports partial_pressure_1 equal to x1 times p1_sat and partial_pressure_2 equal to x2 times p2_sat. The total_pressure field is the sum of those two partial pressures and is the denominator used for vapor fractions. Fields y1 and y2 are the vapor-phase mole fractions; vapor_mole_fractions repeats them as a nested object for clients that prefer a single map. The formula label is always y_i equals x_i times P_i_sat over P, and method is always raoult_vapor_phase_composition so downstream code can branch without sniffing shapes. When both pure vapor pressures are zero, or when both liquid contributions vanish so the sum is exactly zero, the engine refuses the request with invalid_input and a message that states total pressure is zero and vapor-phase mole fractions are undefined—this is the product contract for the zero-pressure edge case rather than returning NaN or infinity. Use partial pressures when you need Dalton-style intermediates for a report; use y1 and y2 alone when a distillation sketch only needs vapor composition; use total_pressure when checking that bubble-point pressure matches a lab measurement in the same units as the pure pressures you supplied.

API usage, pricing, classroom workflows, and practical limits

Call the free in-browser vapor phase composition calculator for homework checks, lecture demos, and quick VLE mental math without installing Aspen, CoolProp, or a local process simulator. Authors shipping SDKs can map y1 and y2 directly into UI tables next to liquid x1 and x2—the same side-by-side layout students draw when they apply Raoult's law by hand on a binary Txy or Pxy sketch. Send a JSON body with the four required fields x1, x2, p1_sat, and p2_sat (or their documented aliases). Use the prepaid API when a tutoring platform, lab notebook service, chemical engineering pipeline, or assessment sandbox needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with a partial-pressure tool when you already know gas mole fractions and total pressure, or with equilibrium-constant utilities when the next step is reaction extents rather than phase split. Keep pure pressures non-negative and within the published magnitude bounds so Worker isolates stay safe.