Question

Freundlich adsorption isotherm is given by the expression $\frac{x}{m}=k{p}^{\frac{1}{n}}$ Which of the following conclusions can be drawn from this expression.

• A. When $n=0,\frac{x}{m}vsp$
  graph is a line parallel to $x-axis$
• B. When $\frac{1}{n}=0,$ the adsorption is independent of pressure.
• C. When $\frac{1}{n}=0,$ the adsorption is directly proportional to pressure .
• D. When $n=0,$ plot of
  $\frac{x}{m}vsp$ is a curve.

Answer 1

Answer: (A), (B)

When $\frac{1}{n}=0,$ the adsorption is independent of pressure.

According to Freundlich isotherm,

the amount of gas adsorbed $\left(x\right)$ per unit mass of solid adsorbent $\left(m\right)$ is related to pressure $\left(P\right)$ at a particular temperature is given by:

$x/m=k.P^{\frac{1}{n}}(n>1)$

So, $\log \left(\frac{x}{m}\right)=\frac{1}{n}(\log P+\log k)$

So, if we plot $\log \left(x/m\right)$ on the $y-axis$ vs. $\log P$ on the $x-axis,$ it comes to be a straight line .

If $1/n=0,\log \left(x/m\right)=\log k,$ so, adsorption becomes independent of pressure.

So, option $\left(A\right)$ is correct but $\left(B\right)$ is wrong.

When $n=0,$ then x/m becomes a constant and the Freundlich isotherm is not followed.

So, $x/mvsp$ graph is a line parallel to the x-axis. So, option $\left(C\right)$ is correct.

If $n=0,$ the plot of $x/mvs.P$ will not be curved since it will be a straight line.

So, option $\left(D\right)$ is wrong.

Hence, options $\left(A\right)$ and $\left(C\right)$ are correct.