Silver tarnishes when exposed to oxygen and dihydrogen mono sulfide, The chemical reaction is as follows: 4Ag(s) + 2H2S(g) + O2--->2Ag2S(s) + 2H2O(l) Every household has some H2S in the air (it smells like rotting eggs), but there is usually only a small quantity. H2S is almost always a limiting reaction, If a silver spoon has 0.0030 moles of tarnish on it, how many moles of H2S was it exposed to?

answer; protein;

  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-

answer: they produce more slow than unicellular organisms.