Final answer:
The unbalanced chemical equation among the provided ones is the fourth equation, H₂ + O₂ → H₂O + H₂O, which should correctly be written as 2H₂ + O₂ → 2H₂O to be balanced.
Step-by-step explanation:
The chemical equation that is unbalanced among the given options is the fourth equation, H₂ + O₂ → H₂O + H₂O. In a balanced chemical equation, the number of atoms of each element on the reactant side must equal the number of atoms of that element on the product side. Let's inspect each of the given equations:
- C + O₂ → CO₂: This equation is balanced as there is one carbon atom on both sides and two oxygen atoms on both sides.
- Sr + O₂ → 2SrO: This equation is unbalanced because there are two oxygen atoms on the reactant side but only one oxygen atom on the product side.
- 6H₂ + 3O₂ → 6H₂O: This equation is balanced with twelve hydrogen atoms and six oxygen atoms present on both sides of the equation.
- H₂ + O₂ → H₂O + H₂O: This equation is not balanced. It features two hydrogen atoms and two oxygen atoms on the reactant side but has four hydrogen atoms and two oxygen atoms on the product side. To balance it, you'd need to make the coefficients consistent: 2H₂ + O₂ → 2H₂O.