An antacid tablet reacts in water, creating bubbles. Which best describes the products of the reaction?
A. A clear gas.
B. A white solid
C. A clear liquid and clear gas
D. A clear liquid
The Correct Answer and Explanation is:
The correct answer is C. A clear liquid and clear gas.
Explanation:
When an antacid tablet dissolves in water, it typically reacts with the water to produce a chemical reaction. Antacid tablets often contain compounds like sodium bicarbonate (NaHCO₃), calcium carbonate (CaCO₃), or magnesium hydroxide (Mg(OH)₂), which react with acids such as hydrochloric acid (HCl) found in the stomach or sometimes in the water, to neutralize the acid and relieve indigestion.
Here’s a breakdown of the reaction:
- Reaction of Sodium Bicarbonate with Water:
A common example is the reaction of sodium bicarbonate with water:
[
NaHCO₃ (aq) \rightarrow Na⁺ (aq) + HCO₃⁻ (aq)
]
The bicarbonate ion (HCO₃⁻) reacts with the water (H₂O) to form carbonic acid (H₂CO₃), which is unstable and decomposes to produce carbon dioxide gas (CO₂) and water:
[
H₂CO₃ \rightarrow CO₂ (g) + H₂O (l)
]
In this case, carbon dioxide gas (CO₂) is released as bubbles, and water remains as the liquid product. - Other Antacid Reactions:
Similar reactions occur with other antacid components. For example, calcium carbonate (CaCO₃) reacts with water to form calcium ions (Ca²⁺), bicarbonate ions (HCO₃⁻), and carbon dioxide gas (CO₂). The carbon dioxide gas is responsible for the bubbling effect. This results in the formation of:
- A clear liquid, which is simply the water or aqueous solution that remains after the reaction.
- A clear gas, which is carbon dioxide (CO₂), a colorless and odorless gas.
Why Not the Other Options?
- A. A clear gas: While carbon dioxide gas is formed, there is also a liquid product (water), so the reaction produces both a gas and a liquid, not just gas.
- B. A white solid: The reaction does not typically produce a solid (except under specific conditions), and antacids are usually designed to dissolve in water.
- D. A clear liquid: Although the liquid is clear, this answer ignores the formation of carbon dioxide gas, which is a key product of the reaction.
Thus, C is the best description, as it accurately reflects both the liquid and gas products of the reaction.