Q.Explain the following:
Freundlich adsorption isotherm, with the help of a graph.

Step 1. State the equation. Freundlich's empirical equation for the adsorption of a gas on a solid, at constant temperature, is $\frac{x}{m} = kP^{1/n}$ (with $n>1$), where $x$ = mass of gas adsorbed, $m$ = mass of adsorbent, $P$ = equilibrium pressure, and $k$, $n$ are constants for that adsorbate-adsorbent-temperature combination.

Step 2. Take logarithms. Taking logarithms of both sides converts the power-law relationship into a linear one: $\log\frac{x}{m} = \log k + \frac{1}{n}\log P$.

Step 3. Interpret as a straight line. Plotting $\log\frac{x}{m}$ (y-axis) against $\log P$ (x-axis) gives a straight line (Fig 11.4), whose slope equals $\frac{1}{n}$ and whose y-intercept equals $\log k$ -- this is how $k$ and $n$ are determined experimentally from a set of adsorption measurements at different pressures. …

Deriving the logarithmic straight-line form of the Freundlich isotherm and describing …

• Plotting x/m vs P directly and calling that graph 'the Freundlich isotherm' -- the characteristic straight line only appears in the log-log plot. …