Answer:
C) Place a 2 in front of CaO
Explanation:
The equation:
Ca2 +O2 → CaO is not balanced as there are 2 atoms of Ca from Ca2 on the left side and there is 1 atom of Ca from CaO on the right side, so add a 2 in front of CaO.
Ca2+O2 → 2CaO
On the left we have:
2 atoms of Ca
2 atoms of O
On the right we have:
2 atoms of Ca
2 atoms of O
The equation is now balanced as there are equal numbers of atoms of each side
