Question

Formic acid, HCOOH, is a weak electrolyte. What solutes are present in an aqueous solution of this compound? Write the chemical equation for the ionization of HCOOH.

Short answer

The solutes present in an aqueous solution of formic acid (HCOOH) are the hydrogen ion (H⁺) and the formate ion (HCOO⁻). The ionization equation for formic acid is: \( HCOOH_{(aq)} \rightleftharpoons H^+_{(aq)} + HCOO^-_{(aq)} \).

Step-by-step solution

Identify the ions produced from the dissociation of formic acid

Let's first identify the ions formed when HCOOH ionizes. Formic acid, HCOOH, is a weak acid that partially dissociates into a hydrogen ion (H⁺) and a formate ion (HCOO⁻).

Write the chemical equation for the ionization of HCOOH

Now we can write the chemical equation for the ionization of formic acid in water: \( HCOOH_{(aq)} \rightleftharpoons H^+_{(aq)} + HCOO^-_{(aq)} \) In this equation, the double arrow (\(\rightleftharpoons\)) indicates that the reaction is reversible, meaning that the ions formed can also recombine to form formic acid. This reversibility is a property of weak electrolytes, as they do not dissociate completely in water. In conclusion, the solutes present in an aqueous solution of formic acid (HCOOH) are the hydrogen ion (H⁺) and the formate ion (HCOO⁻), as shown in the ionization equation: \( HCOOH_{(aq)} \rightleftharpoons H^+_{(aq)} + HCOO^-_{(aq)} \).

Key concepts

Weak Electrolyte

Formic acid, represented by the formula \( \text{HCOOH} \), is classified as a weak electrolyte. But what does this mean, exactly? A weak electrolyte is a substance that only partially dissociates into ions when dissolved in water. Unlike strong electrolytes, which break apart completely, weak electrolytes exist in a dynamic equilibrium between the non-ionized and ionized forms.

This partial dissociation results in fewer ions in the solution, which limits its ability to conduct electricity. In the case of formic acid, when it dissolves in water, only some of the \( \text{HCOOH} \) molecules dissociate into \( \text{H}^+ \) (hydrogen ions) and \( \text{HCOO}^- \) (formate ions). Here’s the chemical equation illustrating this reversible process:

• \( \text{HCOOH}_{(aq)} \rightleftharpoons \text{H}^+_{(aq)} + \text{HCOO}^-_{(aq)} \)

The double arrows in this equation showcase the important concept of reversibility, crucial in understanding weak electrolytes.

Knowing whether a compound is a weak or strong electrolyte helps in predicting its behavior in solution, especially its conducting properties.

Hydrogen Ion

The hydrogen ion, denoted as \( \text{H}^+ \), plays a pivotal role in the ionization of formic acid. When \( \text{HCOOH} \) partially dissociates in water, it releases hydrogen ions. These are simply protons due to their lack of electrons. Given their charge, \( \text{H}^+ \) ions contribute significantly to the acidic nature of the solution.

In the context of formic acid ionization, hydrogen ions:

• Originate from the partial dissociation of the acid \( \text{HCOOH} \)
• Participate in reversible reactions with formate ions to reform \( \text{HCOOH} \)
• Impact the pH level of the solution

This reversible ionization is marked by the double arrow in the equation: \( \text{HCOOH}_{(aq)} \rightleftharpoons \text{H}^+_{(aq)} + \text{HCOO}^-_{(aq)} \).

Understanding the behavior of \( \text{H}^+ \) ions is critical for comprehending acid-base chemistry and even broader chemical reactions involving acids.

Formate Ion

The formate ion, known chemically as \( \text{HCOO}^- \), is one of the key products of formic acid ionization. As formic acid dissociates in water, it generates formate ions along with hydrogen ions. This dissociation is part of a dynamic equilibrium process, characteristic of weak electrolytes.

Here's why formate ions are important:

• They pair with hydrogen ions through reversible reactions back into formic acid.
• Their presence measures the extent of ionization of formic acid.
• They play a role in buffering solutions due to their involvement in reversible reactions.

To really understand formic acid's behavior in solution, it is key to grasp the role of its ions, and the formate ion is central to that understanding. The equation \( \text{HCOOH}_{(aq)} \rightleftharpoons \text{H}^+_{(aq)} + \text{HCOO}^-_{(aq)} \) intricately connects the chemistry of these ions.