Which of the following is the correctly balanced equation for the reaction between hydrogen gas and oxygen gas to form water?

• A. 2H2 + O2 → 2H2O
• B. H2 + O2 → H2O
• C. H2 + 2O2 → 2H2O
• D. 2H2 + 2O2 → 2H2O

Answer: (A)

Verified step by step guidance

1. Identify the reactants and products in the chemical reaction. Here, hydrogen gas (H₂) and oxygen gas (O₂) are the reactants, and water (H₂O) is the product.
2. Write the unbalanced chemical equation using the chemical formulas of the reactants and products: H₂ + O₂ → H₂O.
3. Count the number of atoms of each element on both sides of the equation. Initially, there are 2 hydrogen atoms and 2 oxygen atoms on the reactant side, and 2 hydrogen atoms and 1 oxygen atom on the product side.
4. Balance the equation by adjusting coefficients to ensure the same number of each type of atom on both sides. Start by balancing the oxygen atoms. Since there are 2 oxygen atoms in O₂, you need 2 water molecules to balance the oxygen: H₂ + O₂ → 2H₂O.
5. Finally, balance the hydrogen atoms. With 2 water molecules, there are 4 hydrogen atoms on the product side, so you need 2 H₂ molecules on the reactant side: 2H₂ + O₂ → 2H₂O.