A 2.16-g sample of an oxide of chromium contains 1.34 g of chromium. Calculate the simplest formula for the compound.

chromium:oxygen=1:2  

Explanation:

total mass=2.16g

mass of chromium=1.34g

mass of oxygen=2.16g-1.34g=0.82g

           chromium                                         oxygen

mass:1.34g                                                       0.82

RAM:52                                                            16

divide the mass with the RAM

   0.02577                                                           0.05125

divide by smallest number to find ratio

1                                                                             2

ratio of chromium to oxygen=1:2

  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-

it is the most commonly accepted one