Which of the following chemical equations satisfies the law of conservation of mass?

• A. 2 H_2 + O_2 → 2 H_2O
• B. C + O_2 → CO
• C. Na + Cl_2 → 2 NaCl
• D. N_2 + 2 H_2 → NH_3

Answer: (A)

Verified step by step guidance

1. Understand that the law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction, so the number of atoms of each element must be the same on both sides of the equation.
2. For each given chemical equation, count the number of atoms of each element on the reactant side and compare it to the number on the product side.
3. For example, in the equation \$2\ H_2 + O_2 \rightarrow 2\ H_2O\(, count hydrogen atoms: on the left, \)2 \times 2 = 4\( hydrogens; on the right, \)2 \times 2 = 4\( hydrogens. Count oxygen atoms: on the left, \)2\( oxygens; on the right, \)2 \times 1 = 2$ oxygens. Both sides have equal atoms for each element.
4. Repeat this atom counting process for the other equations: \(C + O_2 \rightarrow CO\), \(Na + Cl_2 \rightarrow 2\ NaCl\), and \(N_2 + 2\ H_2 \rightarrow NH_3\), checking if the atoms balance on both sides.
5. Identify which equation(s) have equal numbers of atoms for every element on both sides, indicating they satisfy the law of conservation of mass.