Q. Which statement is true about this reaction: C6H12O6 6O2 → 6CO2 6H2O

The true statements about the reaction C6H12O6 + 6O2 → 6CO2 + 6H2O include: (1) it represents cellular respiration or glucose combustion, (2) it is an exothermic reaction that releases energy, (3) it is a redox reaction where glucose is oxidized and oxygen is reduced, (4) the carbon in glucose increases in oxidation state while oxygen decreases, and (5) this is essentially the reverse of photosynthesis. This reaction breaks down high-energy glucose molecules using oxygen to produce lower-energy carbon dioxide and water, releasing approximately 686 kilocalories of energy per mole of glucose—energy that living cells capture as ATP or that is released as heat during combustion.

The reaction demonstrates complete oxidation of glucose, which is why it's classified as a combustion reaction when it occurs by burning, or as cellular respiration when it occurs in controlled steps within cells through glycolysis, the Krebs cycle, and the electron transport chain. The stoichiometry shows that oxidizing one glucose molecule requires six oxygen molecules and produces six molecules each of CO2 and H2O, which is why aerobic organisms must continuously take in oxygen and expel carbon dioxide. The reaction is spontaneous and thermodynamically favorable under standard conditions, unlike photosynthesis which requires energy input. This fundamental equation underlies why we need to eat food and breathe oxygen—we're extracting the energy stored in glucose bonds through this oxidation process, making it one of the most important chemical reactions for sustaining life on Earth.