74. Solving a chemistry problem

2. The amount of dye adsorption from solution can be used to estimate the specific surface area of powders. With the introduction of 1 g of activated carbon in 100 ml of an aqueous solution of methylene blue, the dye concentration changes from 10 -4 mol / l to 6 * 10 -5 mol / l, and when 2 g of coal is added to the same initial solution, the equilibrium concentration was 4 * 10 -5 mol/l. Assuming that adsorption is described by the Langmuir equation, calculate the specific surface area of coal. The cross section of the dye molecule is 0.65 nm2.