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In the electrolysis of water, the volume of hydrogen produced is roughly TWICE the volume of oxygen. The reason is best explained by:

AHydrogen is heavier than oxygen
BHydrogen bubbles up faster than oxygen
COxygen reacts with the electrode
DWater has the formula H₂O — two hydrogen atoms for every oxygen atom — so electrolysis releases twice as much hydrogen by volume
Answer & Solution
Correct answer: D. Water has the formula H₂O — two hydrogen atoms for every oxygen atom — so electrolysis releases twice as much hydrogen by volume
In H₂O, hydrogen and oxygen are in a 2:1 ratio. When water is split, this ratio is preserved in the gases released. Since equal volumes of gases at the same temperature/pressure contain equal numbers of molecules (Avogadro), volume of H₂ ≈ 2 × volume of O₂.
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