Fermentation, Glucose, and Ethanol

Alcoholic fermentation: C₆H₁₂O₆ → 2 C₂H₆O + 2 CO₂. One mole of glucose (180.16 g/mol) yields two moles of ethanol C₂H₆O (46.07 g/mol, total 92.14 g) and two moles of carbon dioxide CO₂ (44.01 g/mol, total 88.02 g). Mass is conserved: 180.16 g reactant equals 92.14 + 88.02 g products (within rounding). Students often forget the 1:2 mole ratio for ethanol.

Compare with combustion of glucose in oxygen — complete oxidation to CO₂ and H₂O releases far more energy and different mole ratios. Ethanol fermentation is anaerobic; molar mass still governs how much CO₂ gas volume collects in a fermenter at STP (~22.4 L per mole of CO₂ at 1 atm).

Industrial ethanol blends fuel with gasoline; beverage and sanitizer grades require purity assays by density or GC. Contrast ethanol C₂H₆O with methanol CH₃OH (32.04 g/mol) — similar functional group, lower molar mass, higher toxicity. Sucrose C₁₂H₂₂O₁₁ (342.30 g/mol) hydrolyzes to glucose and fructose before fermentation; total molar mass of monosaccharides equals the disaccharide minus water.