Question

In the unbalanced oxidation-reduction reaction CH₄+O₂→CO₂⁺H₂O, which answer choice below shows the correct, balanced half-reaction for oxygen?

1) O₂ → 2O-
2) O₂ → ₂O₂-
3) O₂ → 4O-
4) O₂ → 4O₂-

Answer 1

The correct balanced half-reaction for oxygen in the given redox reaction is 3) O₂ → 4O⁻. This accounts for oxygen being reduced from O₂ to form two oxide ions, each with a -2 charge.

Step-by-step explanation:

Correct Half-Reaction for Oxygen in a Redox Reaction

To answer the question about the correct balanced half-reaction for oxygen in the unbalanced oxidation-reduction reaction CH4+O2→CO2+H2O, we first need to consider the change in oxidation state for oxygen. Oxygen starts in the O2 molecule with an oxidation state of 0 and is reduced to an oxidation state of -2 in water (H2O). Each oxygen molecule (O2) can produce two oxide ions (O2-), so the correct half-reaction, taking into account the conservation of mass and charge, would be O2 → 4O-, which corresponds to choice 3 from the given options.

By balancing the half-reaction for oxygen, we account for the electrons required for the reduction process. To completely balance the reaction, we would also need to balance hydrogen and carbon atoms, and then finally balance the charges. The overall reaction would be CH4 + 2O2 → CO2 + 2H2O, indicating that one molecule of methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.