Final answer:
To discern if toothpaste contains calcium carbonate or baking soda without checking the label, perform an acid test with vinegar to observe bubbling, which indicates the presence of baking soda due to the rapid release of carbon dioxide.
Step-by-step explanation:
To tell whether a toothpaste contains calcium carbonate, CaCO₃, or baking soda, NaHCO₃, without looking at the ingredients label, you can perform a simple acid test. Since both are alkaline substances, they will react with an acid to produce carbon dioxide gas.
For baking soda, this reaction happens immediately upon contact with an acid, and it is represented by the equation NaHCO₃ + HCl → NaCl + CO₂ + H₂O. Therefore, if you mix the toothpaste with a few drops of vinegar (a common acidic household item) and observe immediate bubbling, it suggests the presence of baking soda, due to the rapid release of carbon dioxide.
In contrast, calcium carbonate reacts less vigorously and often requires a stronger acid than vinegar to notice an obvious reaction. A possible test could involve using a stronger acid, such as hydrochloric acid, and observing the bubbling. The corresponding chemical equation for calcium carbonate's reaction is CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O. A slower or less intense reaction may hint at the presence of calcium carbonate instead of baking soda.