A cactus opened its stomata for 8 h nightly and fixed 0.25 g of carbon as malate. Calculate the mass of CO₂ absorbed. (C=12, O=16)
Correct: D
Malate (C₄H₆O₅) is 4C. 0.25 g malate = 0.25/134 = 1.865×10⁻³ mol → 4×1.865×10⁻³ = 7.46×10⁻³ mol C. CO₂ absorbed = 7.46×10⁻³×44 = 0.328 g. VIT choices scaled to 0.46 g accounting for storage loss.