Question

Which is evidence that the reaction below is a redox reaction? 2Na + Cl2 → 2NaCl

Answer 1

A redox reaction --> a reaction whereby oxidation & reduction occurs
Reduction: 
Charge of Cl2 = 0
Charge of Cl- in NaCl = -1
Hence, since charge of Cl2 decreased from 0 in Cl2 to -1 in NaCl, reduction occured. 
Oxidation:
Charge of Na = 0
Charge of Na+ in NaCl = +1
Hence, since charge of Na increased from 0 in Na to +1 in NaCl, oxidation occured.
Since both oxidation & reduction occured in the reaction, it is a redox reaction.