Which of the following chemical equations is correctly balanced?

• A. H_2 + O_2 → H_2O
• B. 2 H_2 + O_2 → 2 H_2O
• C. H_2 + 2 O_2 → 2 H_2O
• D. 2 H_2 + 2 O_2 → 2 H_2O

Answer: (B)

Verified step by step guidance

1. Identify the number of atoms of each element on both sides of the chemical equation to check if they are equal, which is the requirement for a balanced equation.
2. For the equation \(\mathrm{H_2 + O_2 \rightarrow H_2O}\), count the hydrogen and oxygen atoms on the reactant side and the product side.
3. Adjust the coefficients (the numbers in front of molecules) to balance the number of atoms for each element. Remember, you can only change coefficients, not subscripts within a molecule.
4. For water (\(\mathrm{H_2O}\)), each molecule contains 2 hydrogen atoms and 1 oxygen atom. Use this information to balance hydrogen and oxygen atoms by placing appropriate coefficients before \(\mathrm{H_2}\), \(\mathrm{O_2}\), and \(\mathrm{H_2O}\).
5. Verify that the total number of hydrogen and oxygen atoms are the same on both sides of the equation after adjusting coefficients, confirming the equation is balanced.