Electrolysis of water produces hydrogen and oxygen in the ratio?

Appeared in: HSSC Staff Nurse - 2015

Explanation

The process of electrolysis breaks down water (H₂O) into its constituent elements, hydrogen (H₂) and oxygen (O₂).
The balanced chemical equation for this reaction is 2H₂O(l) → 2H₂(g) + O₂(g).
This equation shows that for every one mole of oxygen gas produced, two moles of hydrogen gas are produced.
According to Avogadro's Law, at the same temperature and pressure, the volume ratio of gases is equal to their molar ratio. Therefore, the volume of hydrogen produced is twice the volume of oxygen, resulting in a 2:1 ratio.

Option A: This ratio is incorrect. It incorrectly suggests that twice as much oxygen is produced as hydrogen. This would be the ratio of oxygen to hydrogen, not hydrogen to oxygen.
Option B: This ratio is not supported by the stoichiometry of the water molecule (H₂O) or the balanced chemical equation for electrolysis.
Option D: This ratio is also incorrect and does not reflect the 2:1 relationship of hydrogen to oxygen atoms within water molecules.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Stoichiometry of water electrolysis as background academic context rather than a clinical decision trigger.
This question tests a fundamental concept in chemistry rather than a direct clinical nursing skill.
Understanding basic scientific principles like electrolysis is part of the foundational knowledge for health sciences.
What if? If the substance being electrolyzed was molten sodium chloride (NaCl), the products would be sodium metal and chlorine gas in a 2:1 molar ratio (2NaCl -> 2Na + Cl2), but the products are not both gases at standard conditions, so a volume ratio is not applicable in the same way.

How to Approach the Question

First, identify the chemical process described: the electrolysis of water.
Recall the chemical formula for water, which is H₂O, indicating two hydrogen atoms for every one oxygen atom.
Write or recall the balanced chemical equation for the decomposition of water: 2H₂O → 2H₂ + O₂.
Analyze the stoichiometry (the molar ratios) of the gaseous products in the balanced equation. The coefficients show 2 moles of H₂ and 1 mole of O₂.
Conclude that the ratio of hydrogen produced to oxygen produced is 2:1.

Concept Tested & Keywords

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