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Reducing chromium(III) to chromium metal requires how many moles of electrons per mole of chromium?
AOne mole
BTwo moles
CSix moles
DThree moles
Answer & Solution
Correct answer: D. Three moles
1. The number of electrons follows directly from the change in oxidation state.
2. Chromium goes from the plus three state to the zero state.
3. The stoichiometry of the chromium(III) reduction process requires three moles of electrons for each mole of chromium(0) produced.
4. That factor of three sets the total charge required for a plating job.
5. Dividing that charge by the current then gives the time needed.
_Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 17 'Electrochemistry', sections 17.1-17.7_
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