Given the equation representing a reaction: 2Ca(s) + O2(g) → 2CaO(s)During this reaction, each elem

August 2019 NY Regents Chemistry Exam

46 Given the equation representing a reaction: 2Ca(s) + O2(g) → 2CaO(s)
During this reaction, each element changes in
(1) atomic number
(2) oxidation number
(3) number of protons per atom

(4) number of neutrons per atom

Solution: This is a redox reaction since Ca has an oxidation number of 0 as a reactant and +2 as a product. Similarly, oxygen goes from 0 to -2. Each elements changes in oxidation number.

Answer: 2

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