Which equation has the form ln(Psat) = A - B/(T+C)?

Which equation has the form ln(Psat) = A - B/(T+C)?

• A. Clausius-Clapeyron equation
• B. Raoult's Law
• C. Antoine's Equation
• D. Van't Hoff equation

Answer: (C)

The form given matches an Antoine-type equation. This empirical correlation expresses saturated vapor pressure as a function of temperature using a logarithm of Psat equal to a constant minus another constant divided by (temperature plus an offset). The constants A, B, and C are fitted for each substance, and the use of the temperature shift (T + C) improves the fit over a practical range. Changing the logarithm base (natural log vs base-10) is just a matter of constants being redefined, not a change in the underlying idea. This is different from the Clausius-Clapeyron relation, which links ln Psat to 1/T without a T offset; Raoult's Law describes how a component's partial pressure depends on mole fraction and its pure-component pressure; and the Van't Hoff equation relates equilibrium constants to 1/T. The given form is the hallmark of the Antoine equation.

The form given matches an Antoine-type equation. This empirical correlation expresses saturated vapor pressure as a function of temperature using a logarithm of Psat equal to a constant minus another constant divided by (temperature plus an offset). The constants A, B, and C are fitted for each substance, and the use of the temperature shift (T + C) improves the fit over a practical range. Changing the logarithm base (natural log vs base-10) is just a matter of constants being redefined, not a change in the underlying idea.

This is different from the Clausius-Clapeyron relation, which links ln Psat to 1/T without a T offset; Raoult's Law describes how a component's partial pressure depends on mole fraction and its pure-component pressure; and the Van't Hoff equation relates equilibrium constants to 1/T. The given form is the hallmark of the Antoine equation.