The oxidation of ammonia produces nitrogen and water via the reaction below. 4 NH3 3 O2 --> 2 N2 6 H2O If the rate of formation of N2 is 2.0 M/s, then what is the rate at which H2O is being formed

  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-

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.