For a reaction at equilibrium, which of the following is the best way to think about it?

a. forward rate = reverse rate
b. the concentration of intermediates becomes negligible.
c. the concentration of reactants becomes negligible.
d. the concentration of reactants = concentration of products.
e. the concentration of reactants and products are not related.

Option A. forward rate = reverse rate

Explanation: for a system to be in dynamic equilibrium, it means that the rate of formation of product is the same as the rate of formation of reactant.

  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-