CHM-22

Fugacity snapshot f = φ p

f = φ p. Effective pressure that restores the ideal-gas μ formula.

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NonidealityLewis fugacity

Governing equation

f=\varphi p

$p \in \left[1, 20000\right]$

where

\varphi: Fugacity coefficient (—)
p: Pressure (kPa)
f: Fugacity (kPa)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

f=\varphi p

$p \in \left[1, 20000\right]$

$p = 1$ $f = 0.85$

Along the curve

②

Domain of the variable — blue

p_{\min} = 1,\quad p_{\max} = 20000

$p \in \left[1, 20000\right]$

$p = 1$ $p = 1$

Along the curve

③

Response curve — green

f=\varphi p

$p \in \left[1, 20000\right]$

$p = 1$ $f = 0.85$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}f}{\mathrm{d}p}

$p \in \left[1, 20000\right]$

$p = 126.8$ $f^{\prime} = 0.85$

Along the curve

Lecture brief

Historical brief

Ideal-gas law, van ’t Hoff, Nernst, Michaelis–Menten and Clausius–Clapeyron are physical chemistry’s working equations of equilibrium and rate. The lab is pressure, potential and kinetics. This sheet (CHM-22 — Fugacity snapshot f = φ p) is the form associated with Lewis fugacity. Working symbols: $\varphi$ , $p$ $\rightarrow$ $f$ . φ → 1 as p → 0. Corresponding-states charts give φ(Tr, Pr).

Purpose

Purpose: compute

f

from

\varphi

p

in Physical chemistry via

f=\varphi p

f = φ p. Effective pressure that restores the ideal-gas μ formula. Use it when a real physical chemistry question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

\varphi = 0.850\,\mathrm{—}

p = 500.000\,\mathrm{kPa}

, the governing relation

f=\varphi p

yields

f = 425.00\,\mathrm{kPa}

. Enter a compressibility-derived fugacity coefficient. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Fugacity coefficient \varphi0.85 —Pressure p500 kPa

Outputs

Fugacity f425.00 kPa

Reading speed

Watch on YouTube

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Narration of this film

Enter a compressibility-derived fugacity coefficient.

φ → 1 as p → 0. Corresponding-states charts give φ(Tr, Pr).

Reading speed

Watch on YouTube