Question

Milk of magnesia is an over-the-counter product that is used to neutralize excess stomach acid. (a) Look up the active ingredient in milk of magnesia. (b) Stomach acid is predominantly hydrochloric acid. Write the balanced chemical equation for the neutralization reaction between \(\mathrm{HCl}\) and the active ingredient from part (a).

Short answer

The active ingredient is \( \mathrm{Mg(OH)_2} \); balanced equation: \( \mathrm{Mg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O} \).

Step-by-step solution

Identifying the Active Ingredient

The active ingredient in milk of magnesia is magnesium hydroxide, with the chemical formula \( \mathrm{Mg(OH)_2} \).

Writing the Reactants

The stomach acid is primarily hydrochloric acid, which has the chemical formula \( \mathrm{HCl} \). We are reacting \( \mathrm{Mg(OH)_2} \) with \( \mathrm{HCl} \).

Determining the Products

The reaction between \( \mathrm{Mg(OH)_2} \) and \( \mathrm{HCl} \) forms magnesium chloride \( \mathrm{MgCl_2} \) and water \( \mathrm{H_2O} \).

Balancing the Equation

The unbalanced reaction is: \[ \mathrm{Mg(OH)_2 + HCl \rightarrow MgCl_2 + H_2O} \]To balance the equation, ensure the same number of each type of atom on both sides:- The balanced equation is \( \mathrm{Mg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O} \).

Key concepts

Magnesium Hydroxide

Milk of magnesia is commonly used to alleviate symptoms caused by excess stomach acid. The key component responsible for this effect is magnesium hydroxide, represented by the chemical formula \( \mathrm{Mg(OH)_2} \). Magnesium hydroxide works as an antacid because it reacts with hydrochloric acid, which is the main component of stomach acid, to form a neutralization reaction.
This ingredient exists as a milky white suspension when combined with water due to its low solubility in water. Despite its limited solubility, it's quite effective in balancing stomach acid levels. Magnesium hydroxide not only neutralizes excess acid, relieving symptoms like heartburn and indigestion, but it also acts as a laxative by attracting water in the colon, which helps to soften stools.
Keep in mind that while magnesium hydroxide is useful for immediate relief, continuous overuse can lead to other issues due to its laxative effect. Also, it is important to follow dosage instructions on medication labels.

Chemical Equation Balancing

Balancing chemical equations is an essential skill in chemistry to understand the reactants' transformation into products. It ensures that both the Law of Conservation of Mass and atomic balance are respected during a chemical reaction.
Let's consider the neutralization reaction between magnesium hydroxide \( \mathrm{Mg(OH)_2} \) and hydrochloric acid \( \mathrm{HCl} \). Initially, your reaction might not be balanced: \[ \mathrm{Mg(OH)_2 + HCl \rightarrow MgCl_2 + H_2O} \] At this point, you have to ensure the same number of each type of atom on both sides of the equation.

• The left side initially has one magnesium (Mg), two hydroxide ions (OH), and one chlorine (Cl).
• The right side has one magnesium, two chloride ions, and two water molecules.

To balance this reaction, adjust the coefficients in front of each compound, ensuring an equal number of each atom appears on both sides:
Thus, the balanced equation is: \[ \mathrm{Mg(OH)_2 + 2HCl \rightarrow MgCl_2 + 2H_2O} \]
This balanced equation shows that one molecule of magnesium hydroxide reacts with two molecules of hydrochloric acid, forming one molecule of magnesium chloride and two molecules of water.

Stomach Acid Neutralization

Stomach acid neutralization plays a crucial role in the digestion process and maintaining the health of the digestive tract. The stomach naturally produces hydrochloric acid \( \mathrm{HCl} \) essential for digestion and defense against pathogens. However, when overproduced, it can lead to discomforts such as heartburn or indigestion.
Neutralization occurs when a base like magnesium hydroxide interacts with the acidic hydrogen chloride in the stomach. The reaction forms water \( \mathrm{H_2O} \) and a salt, magnesium chloride \( \mathrm{MgCl_2} \), reducing acidity levels.

• This process helps alleviate symptoms associated with excess stomach acid.
• The produced products, water, and magnesium chloride, are easily handled by the body without causing further irritation.

Neutralization reactions are crucial therapeutic strategies in managing conditions like gastroesophageal reflux disease (GERD) and other acid-related conditions. Therefore, understanding these basic chemical principles can offer insights into how common medications like milk of magnesia function in easing digestive discomforts.