Reaction A: 6CO2(g) + 6H2O(l) + sunlight → C6H12O6(aq) + 6O2(g) Reaction B: 2H2(g) + O2(g) → 2H2O(g) + energy A. Reactions A and B are both exothermic. B. Reaction A is endothermic, and reaction B is exothermic. C. Reactions A and B are both endothermic. D. Reaction A is exothermic, and reaction B is endothermic.

  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-