Final answer:
The missing reactant X that when reacts with sulfuric acid produces salt, water, and carbon dioxide is sodium carbonate (Na₂CO₃). So the answer is C. Sodium carbonate.
Step-by-step explanation:
When a chemical reaction involving sulfuric acid is taking place and the products are salt, water, and carbon dioxide, the missing reactant X is most likely a carbonate compound, since carbonates react with acids to release carbon dioxide.
Given the options, sodium carbonate (Na₂CO₃) would react with sulfuric acid (H₂SO₄) to form a salt (sodium sulfate:
Na₂SO₄), water (H₂O), and carbon dioxide (CO₂). So the correct answer is C. Sodium carbonate.
This can be represented as follows :
H₂SO₄ (aq) + Na₂CO₃ (aq) → Na₂SO₄ (aq) + CO₂ (g) + H₂O (l).