CHM-11

Henry's law

p = kH x. Solubility of a dilute gas in a liquid.

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SolutionsHenry 1803

Governing equation

p=k_H x

$x \in \left[1\times 10^{-8}, 0.05\right]$

where

k_H: Henry constant (kPa)
x: Mole fraction (—)
p: Partial pressure (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

p=k_H x

$x \in \left[1\times 10^{-8}, 0.05\right]$

$x = 1\times 10^{-8}$ $p = 0.002$

Along the curve

②

Domain of the variable — blue

x_{\min} = 1\times 10^{-8},\quad x_{\max} = 0.05

$x \in \left[1\times 10^{-8}, 0.05\right]$

$x = 1\times 10^{-8}$ $x = 1\times 10^{-8}$

Along the curve

③

Response curve — green

p=k_H x

$x \in \left[1\times 10^{-8}, 0.05\right]$

$x = 1\times 10^{-8}$ $p = 0.002$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}p}{\mathrm{d}x}

$x \in \left[1\times 10^{-8}, 0.05\right]$

$x = 3.14\times 10^{-4}$ $p^{\prime} = 1.6\times 10^{5}$

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-11 — Henry's law) is the form associated with Henry 1803. Working symbols: $k_H$ , $x$ $\rightarrow$ $p$ . The Henry constant kH has many unit conventions. Here p = kH x with kH in kPa.

Purpose

Purpose: compute

p

from

k_H

x

in Physical chemistry via

p=k_H x

p = kH x. Solubility of a dilute gas in a liquid. 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

k_H = 160000.000\,\mathrm{kPa}

x = 2.000e-4\,\mathrm{—}

, the governing relation

p=k_H x

yields

p = 32.000\,\mathrm{kPa}

. Infinite-dilution solute, isothermal. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Henry constant k_H160000 kPaMole fraction x0.0002 —

Outputs

Partial pressure p32.000 kPa

Reading speed

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Narration of this film

Infinite-dilution solute, isothermal.

The Henry constant kH has many unit conventions. Here p = kH x with kH in kPa.

Reading speed

Watch on YouTube