The following data were obtained in a BET apparatus for adsorption equilibrium of N₂ on silica gel (SG) at –195.8°C. Estimate Sg in m²/g of silica gel. How does your value compare with that in Table 15.2?

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Table 15.2 Representative Properties of Commercial Porous Adsorbents Adsorbent Activated alumina Silica gel: Small pore Large pore Activated carbon: Small pore Large pore Molecular-sieve carbon Molecular-sieve zeolites Polymeric adsorbents Nature Hydrophilic, amorphous Hydrophilic/hydrophobic, amorphous Hydrophobic, amorphous Pore Diameter dp, A 10-75 22-26 100-150 10-25 >30 Hydrophobic 2-10 Polar-hydrophilic, crystalline 3-10 40-25 Particle Porosity, Ep 0.50 0.47 0.71 0.4-0.6 0.2-0.5 0.4-0.55 Particle Density Pp, g/cm³ 1.25 1.09 0.62 0.5-0.9 0.6-0.8 0.98 1.4 Surface Area Sg, m²/g 320 750-850 300-350 400-1200 200-600 400 600-700 80-700 Capacity for H₂O Vapor at 25°C and 4.6 mmHg, wt% (Dry Basis) 7 11 - 118 20-25