Which equation obeys the law of conservation of
mass?
H₂(g) + O₂(g) →→ H₂O(g)
H₂(g) + O₂(g) →→ H₂O(g) +4He(g)
O2H₂(g) + O₂(g) → 2H₂O(g)
H₂(g) → H₂O(g)
H₂(g) + O₂(g) → 2H₂O(g)