Question

If you had a "sour stomach," you might try an over-the-counter antacid tablet to relieve the problem. Can you think of evidence that the action of such an antacid is a chemical reaction?

Short answer

In conclusion, the action of an antacid tablet is a chemical reaction, evidenced by the release of carbon dioxide gas as bubbles, change in temperature, and the possible formation of a precipitate. This chemical reaction occurs when the alkaline substances in the tablet, such as calcium carbonate, react with stomach acid (hydrochloric acid) to neutralize excess acidity and provide relief from a sour stomach.

Step-by-step solution

Reminder: Indicators of Chemical Reactions

Common indicators of a chemical reaction include: color change, formation of a precipitate, evolution of gas, temperature change, and production of light. We'll use these indicators to find evidence supporting the idea that the action of antacid tablets is a chemical reaction.

1. Investigate the ingredients of antacid tablets

Most antacid tablets contain a mixture of substances, including carbonates or hydroxides of alkaline earth metals (such as calcium carbonate or magnesium hydroxide) that react with stomach acids (hydrochloric acid) to neutralize the excess acidity. Other ingredients may include various excipients and binders.

2. Reaction between the alkaline substance and stomach acid

When an antacid tablet is taken, the alkaline substances in it react with the stomach acid (hydrochloric acid). This reaction can be represented as follows: \[ 2 HCl(aq) + CaCO_3(s) \rightarrow CaCl_2(aq) + H_2O(l) + CO_2(g) \] The released carbon dioxide gas can be observed in the form of bubbles, which is evidence of a chemical reaction.

3. Temperature change

During the reaction between the alkaline substances and stomach acids, heat may be either absorbed or released. This change in temperature is another indication of a chemical reaction. In some cases, the antacid tablets might feel warm or cold upon reaction, providing evidence of a chemical reaction.

4. Formation of a precipitate

Although not common for most antacid tablets, in some cases, the reaction between the tablet and stomach acid may produce a solid substance (precipitate), which is another indicator of a chemical reaction. In conclusion, the evidence that shows the action of an antacid tablet is a chemical reaction includes the release of carbon dioxide gas, the change in temperature, and the possible formation of a precipitate. All these factors contribute to the neutralization of excess stomach acid and provide relief from a sour stomach.

Key concepts

Indicators of Chemical Reactions

Understanding the indicators of chemical reactions is crucial for identifying whether a chemical change is occurring. These indicators include observable changes that can signify a reaction has taken place. For example:

• Color Change: A change in color can indicate a chemical bond has been made or broken within a substance.
• Formation of a Precipitate: The creation of a solid from two liquids during a reaction is a clear indicator.
• Evolution of Gas: The production of a gas, often seen as bubbles, shows a reaction is occurring.
• Temperature Change: Heat absorbed or released is a strong sign of a chemical process.
• Production of Light: Some reactions emit light as a product of their occurrence.

When observing antacid tablets reacting with stomach acid, these indicators can help determine the chemical reactions taking place, providing evidence for the antacid's mode of action.

Neutralization Reaction

A neutralization reaction is a type of chemical reaction in which an acid and a base react to form water and a salt. This reaction is essential in the context of antacids because it directly relates to how they alleviate the discomfort caused by excess stomach acid. The antacid substances commonly contain bases such as calcium carbonate \(CaCO_3\) or magnesium hydroxide \(Mg(OH)_2\).

When these bases come into contact with hydrochloric acid \(HCl\), found in the stomach, the following neutralization reaction typically occurs:
\[ 2 HCl(aq) + CaCO_3(s) \rightarrow CaCl_2(aq) + H_2O(l) + CO_2(g) \]
This reaction results in the production of calcium chloride \(CaCl_2\), water \(H_2O\), and carbon dioxide gas \(CO_2\), effectively reducing the acidity in the stomach by neutralizing the \(HCl\).

Stomach Acid and Antacids

The human stomach produces gastric acid, primarily composed of hydrochloric acid \(HCl\), which assists in the digestion of food. However, when the stomach produces too much acid, it can cause discomfort known as acid indigestion or a sour stomach. Antacids are over-the-counter medications designed to counteract the excess acidity.

Antacids contain alkaline compounds such as magnesium hydroxide or calcium carbonate, which react with the excess \(HCl\) in the stomach, neutralizing its acidity through a chemical reaction. This not only helps relieve the discomfort but also illustrates a practical application of a neutralization reaction. The efficacy of antacids is a direct result of their chemical reactions with stomach acid.

Chemical Reaction Evidence

Evidence of a chemical reaction can range from visible cues to more subtle indicators. When we drop an antacid tablet into the stomach, the chemical reaction's evidence can be seen and felt.

• The effervescence or bubbling observed is due to the release of \(CO_2\) gas, a clear evidence that a reaction is taking place.
• A temperature change may also occur; for instance, the mixture might feel warmer due to the exothermic nature of the reaction.
• Although less common, the formation of a precipitate could also serve as evidence, indicating the production of an insoluble salt.

In each case, the evidence is linked to the reaction between the antacid's active ingredients and the stomach acid. Each indicator is a piece of the puzzle, confirming the occurrence of a chemical reaction and the tablet's action to neutralize stomach acidity.