Apentix/AP Chemistry/Unit 9: Applications of Thermodynamics/Question
AP Chemistrymediummcq1 pt

Why are all standard reduction potentials reported relative to the standard hydrogen electrode (SHE)?

A.Absolute single-electrode potentials cannot be measured, so the SHE is assigned exactly 0 V as a universal reference
B.The SHE produces the largest potential of any half-cell
C.Hydrogen was assigned zero because its potential never changes with conditions
D.The reference applies only to half-reactions that involve gases

Explanation

Core Concept

A voltmeter reads only differences between two electrodes; there is no way to probe one half-cell alone. Chemists fixed the scale by defining the SHE, 2 H⁺ + 2 e⁻ → H₂ at 1 M, 1 bar, and 25 °C, as exactly 0.000 V. Every tabulated E° is then a measured voltage against that anchor, and positive values flag couples stronger than H⁺ at oxidizing.

Correct Answer

AAbsolute single-electrode potentials cannot be measured, so the SHE is assigned exactly 0 V as a universal reference

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