Question

What is the BET surface area of activated carbon with a monolayer capacity of 25 mg/g and a multilayer capacity of 90 mg/g, given that the weight of the activated carbon used for the experiment was 5 g?

Answer 1

To calculate the BET surface area of the activated carbon, we can use the BET equation:BET surface area  S_BET  =  V_m * N_A * A_m  /  M where:- V_m is the monolayer capacity  in this case, 25 mg/g - N_A is Avogadro's number  6.022 x 10^23 molecules/mol - A_m is the cross-sectional area of the adsorbate molecule  for nitrogen, it is 0.162 nm - M is the molar mass of the adsorbate molecule  for nitrogen, it is 28.02 g/mol First, we need to find the amount of adsorbate in the monolayer. Since the activated carbon has a monolayer capacity of 25 mg/g and we have 5 g of activated carbon, the amount of adsorbate in the monolayer is:Amount of adsorbate = 25 mg/g * 5 g = 125 mgNow we can calculate the BET surface area:S_BET =  125 mg * 6.022 x 10^23 molecules/mol * 0.162 nm  /  28.02 g/mol First, convert the amount of adsorbate to moles:125 mg *  1 g / 1000 mg  *  1 mol / 28.02 g  = 0.00446 molNow, plug this value back into the BET equation:S_BET =  0.00446 mol * 6.022 x 10^23 molecules/mol * 0.162 nm  /  1 S_BET = 4.36 x 10^22 nmTo convert the surface area to m, use the conversion factor:1 nm = 10^-18 mS_BET = 4.36 x 10^22 nm *  10^-18 m / 1 nm  = 436 mSo, the BET surface area of the activated carbon is approximately 436 m.