5 molecules of water are formed.
1 Oxygen atom is left over.
Explanation:
Hydrogen reacts with oxygen to form water.
H₂ + O₂ - H₂O
We need to balance the above equation. On balancing we get,
2H₂ + O₂ - 2H₂O
When 3 O₂ molecule reacts with 5H₂O, then the equation becomes
5H₂ + 3O₂ - 5H₂O + O
5 molecules of water are formed.
1 Oxygen atom is left over.