To determine the surface area of the porous material using the BET Brunauer-Emmett-Teller method, we need to know the volume of nitrogen gas adsorbed at the monolayer formation Vm and the cross-sectional area of a nitrogen molecule . The cross-sectional area of a nitrogen molecule is approximately 0.162 nm.To find the volume of nitrogen gas adsorbed at the monolayer formation Vm , we need to analyze the adsorption isotherm data. The data should be plotted as a BET plot, which is a linear plot of P/ V P0-P versus P/P0, where P is the equilibrium pressure, V is the volume of gas adsorbed, and P0 is the saturation pressure. The slope and intercept of the linear region of the plot can be used to calculate Vm using the following equation:Vm = slope * intercept / slope - intercept Once Vm is determined, the surface area S of the porous material can be calculated using the following equation:S = Vm * N * / NAwhere N is the Avogadro's number 6.022 x 10 molecules/mol and NA is the molar volume of the adsorptive gas for nitrogen, NA is approximately 22.4 L/mol at standard temperature and pressure .By plugging in the values of Vm, N, , and NA into the equation, we can calculate the surface area of the porous material.