The mass of gas adsorbed, $x$, per unit mass of adsorbate, m, was measured at various pressures, p. A graph between $\log \frac{x}{m}$ and $\log$ $p$ gives a straight line with slope equal to 2 and the intercept equal to $0.4771$. The value of $\frac{x}{m}$ at a pressured of $4 atm$ is :

(Given $\log 3=0.4771)$

According to Freundlich Isotherm it can be written as,

$\log \frac{x}{m}=\log K+\frac{1}{n}\log P$

According to the above Freundlich Isotherm equation, slope and intercept are $\frac{1}{n} and \log k$ respectively, hence 

$$\begin{gathered} \frac{1}{\mathrm{n}}=2 \\ \log \mathrm{k}=0.4771 \\ \mathrm{k}=3 \end{gathered}$$

Determining the value of $\frac{x}{m}$ at 4 atm pressure, using another equation of Freundlich Isotherm:

$\frac{x}{m}=K{P}^{\frac{1}{n}}$

Substitute the values:

$\frac{x}{m}=3\times 4^2=48$

Hence the value of $\frac{x}{m}$ will be $48$.