Simplified redox equation for dichromate reduction by ethanol

Steps:

• Note the oxidation half-equation releases 2H+ and 2e- from one ethanol to ethanal.
• Recall the dichromate reduction half-equation: Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O.
• Combine for simplest integer ratio, but use single-molecule form for illustration in organic contexts.
• Select the option showing core reactants/products with minimal H⁺ under acidified conditions.

Why A is correct:

• Matches the standard simplified form for teaching the reaction, where one H⁺ represents the acidified medium tying to the dichromate reduction formula.

Why the others are wrong:

• B incorrectly specifies 2H⁺, mismatching the single H⁺ needed in simplified acid role.
• C uses excessive coefficients (14H⁺, 6 ethanol), intended for full balancing but wrong for partial oxidation stoichiometry.
• D duplicates A exactly, offering no distinct equation.

Final answer: A