Answer
Any half-reaction in an activity series will be spontaneous when paired with the reverse of any half reaction below it.
Work Step by Step
This holds true for all half-reactions and follows the trend of reactivity down the activity series.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.