The mass of gas adsorbed, x, per unit mass of adsorbate, m, was measured at various pressures, p. A graph between log x/m and log p gives a straight line with slope equal to 2 and the intercept equal to 0.4771. The value of x/m at a pressure of 4 atm is :
(Given log 3 = 0.4771)

Solution

Chemistry ma’am · 4 steps

Read the Freundlich log plot: the intercept gives k, the slope gives 1/n, and then you just plug in p.

1. Freundlich in log form. The Freundlich isotherm is x/m = k p^(1/n). Taking log of both sides turns it into a straight line of log x/m against log p.

   log x/m = log k + 1/n log p

2. Match the graph. The slope is 1/n = 2. The intercept is log k = 0.4771 = log 3, so k = 3.
3. Put in p. At p = 4 atm, x/m = 3 × 4² = 3 × 16.
4. So. x/m = 48.

The common slip: 6. Taking the slope as n instead of 1/n makes the power 1/2 and gives 3 × 4^(1/2) = 6, not 48.

The idea to keep. On a Freundlich log plot, the slope is 1/n (the power on p) and the intercept is log k. Take the antilog of the intercept before you use it.

Answer from the NTA final answer key. Solution by PrepWiser.