Which of the following chemical equations best supports the law of conservation of mass?

• A. 2H_2 + O_2 ightarrow 2H_2O
• B. Na + Cl_2 ightarrow NaCl_2
• C. N_2 + 3H_2 ightarrow 2NH_3 + H_2
• D. C + O_2 ightarrow CO

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. This means the number of atoms of each element must be the same on both sides of the equation.
2. Step 2: For each 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. Step 3: Check the equation \$2H_2 + O_2 \rightarrow 2H_2O\(: On the left, there are 4 hydrogen atoms (from \)2H_2\() and 2 oxygen atoms (from \)O_2\(). On the right, there are 4 hydrogen atoms (from \)2H_2O\() and 2 oxygen atoms (from \)2H_2O$). The atoms balance.
4. Step 4: Examine the other equations similarly to see if the atoms balance. For example, \(Na + Cl_2 \rightarrow NaCl_2\) has 1 sodium atom on the left but 1 on the right, but chlorine atoms are 2 on the left and 2 on the right, so check if the formula \(NaCl_2\) is chemically correct and balanced.
5. Step 5: Identify the equation where the number of atoms for each element is equal on both sides, confirming it supports the law of conservation of mass.