Which of the following is true of the the law of conservation of energy? Energy is not created nor destroyed except with the addition of oxygen Energy is not created or destroyed under ordinary conditions, but it may be changed from one form to another Matter may be changed from one form to another under ordinary conditions but cannot be created or destroyed, except in nuclear reactions Matter can only be created with the addition of oxygen None of the answer choices are correct.

  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-

there are two significant figures.

the answer is a! (2.9 x 10^-18 j) hope i could someone. : )