Question

One ingredient in some antacids is \(\mathrm{Mg}(\mathrm{OH})_{2}\). a. If the base is not very soluble in water, why is it considered a strong base? b. What is the neutralization reaction of \(\mathrm{Mg}(\mathrm{OH})_{2}\) with stomach acid, \(\mathrm{HCl}\) ?

Short answer

a. A strong base completely dissociates in water; b. \(\text{Mg(OH)}_2 + 2 \text{HCl} \rightarrow \text{MgCl}_2 + 2 \text{H}_2\text{O}\).

Step-by-step solution

Understanding Strong Bases

A strong base is a substance that completely dissociates into its ions in water. Even if \(\text{Mg(OH)}_2\) is not very soluble, the part that does dissolve will completely dissociate into \(\text{Mg}^{2+} \) and \(\text{OH}^{-} \) ions. This complete dissociation is why it is considered a strong base.

Balancing the Neutralization Reaction

To find the neutralization reaction between \(\text{Mg(OH)}_2\) and \(\text{HCl}\), first write down the reactants: \(\text{Mg(OH)}_2\) and \(\text{HCl}\). Magnesium hydroxide reacts with hydrochloric acid to produce water and magnesium chloride. The balanced equation is: \[ \text{Mg(OH)}_2 + 2 \text{HCl} \rightarrow \text{MgCl}_2 + 2 \text{H}_2\text{O} \]

Identify Products

The products of the neutralization reaction are magnesium chloride (\(\text{MgCl}_2\)) and water (\(\text{H}_2\text{O}\)).

Key concepts

strong base

A strong base is defined by its ability to completely dissociate in water. This means that when a strong base dissolves, it separates entirely into its constituent ions.

Even if magnesium hydroxide \(\text{Mg(OH)}_2\) is not very soluble, the small amount that does dissolve will fully dissociate into magnesium ions \(\text{Mg}^{2+}\) and hydroxide ions \(\text{OH}^-\).

This complete dissociation makes \(\text{Mg(OH)}_2\) effective in neutralizing acids, thus classifying it as a strong base.

dissociation

Dissociation refers to the process where a compound breaks down into its individual ions when dissolved in water.

For example, when \(\text{Mg(OH)}_2\) dissolves, it splits into \(\text{Mg}^{2+}\) and \(\text{OH}^-\) ions.

Here’s how it works:

• The ionic bonds between magnesium and hydroxide ions are broken by water molecules.
• This results in the formation of free \(\text{Mg}^{2+}\) and \(\text{OH}^-\) ions.

This process is key to the behavior of strong bases in water.

balancing chemical equations

Balancing chemical equations is essential for understanding reactions. It ensures that the number of atoms for each element is the same on both sides of the equation.

For the reaction between \(\text{Mg(OH)}_2\) and \(\text{HCl}\), the balanced equation is:

\[ \text{Mg(OH)}_2 + 2 \text{HCl} \rightarrow \text{MgCl}_2 + 2 \text{H}_2\text{O} \] Steps to balance:

• Write down the reactants and products first.
• Ensure that the number of atoms for each element is the same on both sides.
• Adjust coefficients as necessary to balance the equation.

In this case, adding a coefficient of 2 before \(\text{HCl}\) and \(\text{H}_2\text{O}\) balances the equation.

chemical reactions

Chemical reactions involve the transformation of reactants into products. In the neutralization reaction of \(\text{Mg(OH)}_2\) with \(\text{HCl}\), new substances form as atoms rearrange.

The main steps are:

• Reactants \(\text{Mg(OH)}_2\) and \(\text{HCl}\) mix.
• Magnesium ions, hydroxide ions, and hydrogen ions interact.
• Magnesium chloride \(\text{MgCl}_2\) and water \(\text{H}_2\text{O}\) form as products.

This process is typical in many chemical reactions involving acids and bases.

acid-base chemistry

Acid-base chemistry focuses on the behavior of acids and bases during reactions.

In the neutralization reaction:

• Acids, like \(\text{HCl}\), donate protons (H⁺ ions).
• Bases, like \(\text{Mg(OH)}_2\), accept protons or donate hydroxide ions (OH⁻ ions).

The general result:

An acid and a base react to form water and a salt. In our case,
\[ \text{Mg(OH)}_2 + 2 \text{HCl} \rightarrow \text{MgCl}_2 + 2 \text{H}_2\text{O} \] Water forms from the combination of H⁺ ions from the acid and OH⁻ ions from the base.