Question

The adsorption isotherm for a gas is given by the relation $x=ap/(1+bp)$ where $x$ is moles of gas adsorbed per gram of the adsorbent, $p$ is the pressure of the gas, and $a$ and $b$ are constants. Then $x$:

• A. increases with $p$
• B. remains unchanged with $p$
• C. decreases with $p$
• D. increases with $p$ at low pressures and then remains the same at high pressures

Answer 1

The correct option is D increases with $p$ at low pressures and then remains the same at high pressures

$\begin{array}{c}\text{At low pressure the equation changes into}\\ \\ x=ap\Rightarrow x\propto p\\ \\ \text{At high pressures}\\ \\ x=\frac{ap}{bp}=\frac{a}{b}\Rightarrow x=\text{constant}\\ \\ \text{Therefore}x\text{increases with}p\text{at low pressues and then remains the same at high pressure.}\end{array}$