August 2019 NY Regents Chemistry Exam
24 When a sample of Mg(s) reacts completely with O2(g), the Mg(s) loses 5.0 moles of electrons. How many moles of electrons are gained by the O2(g)? (1) 1.0 mol
(2) 2.5 mol (3) 5.0 mol
(4) 10.0 mol
Solution: In a balanced redox reaction, the number of moles of electrons lost by one element is equal to the number of moles of electrons gained by another element.
Answer: 3
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