The reaction 2Mg(s) + O2(g) --> 2MgO(s) is a Group of answer choices
double-replacement reaction.
decomposition reaction.
synthesis reaction.
single-replacement reaction.

Double-Replacement Reaction

Explanation:

Mg is Oxidized, and O2 is the cause of the oxidation, hence the Oxidizing agent.  That means that O2 is Reduced and Mg is the cause naming it the Reducing agent.

OIL - RIG   Oxidation is Loss-Reduction is Gain

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-