The question aims to find the solute particles of the formic acid in an aqueous solution and the chemical equation for its ionization in water.
This question is based on the concept of ionization of electrolytes. Weak electrolytes are known to not completely ionize in water. The weak electrolytes will contain ions and molecules in the aqueous solution when added to water. In contrast, the strong electrolyte will completely dissolve in water with $100\%$ ionization. When added to water, weak electrolytes will only ionize around $1\%$ to $10\%$. Examples of weak electrolytes are acetic acid $(CH_3COOH)$, carbonic acid $(H_2CO_3)$, ammonia $(NH_3)$ and phosphoric acid $(H_3PO_4)$.
Formic acid is a weak electrolyte and a simple carboxylic acid with a single carbon atom. It has a pungent odor and exists in the form of colorless liquid. It is corrosive to metals and tissues. Its molecular formula is given as:
\[ Formic\ Acid\ \longrightarrow CH_2O_2\ or\ HCOOH \]
Expert Answer
Formic acid is a weak electrolyte, which means that it will not fully dissociate in water. This will result in the formic acid being broken down into its ions. The constituents of formic acid will be present in the form of anion and cation. The constituents of $HCOOH$ are given as:
\[ HCOOH \Rightarrow H^{+}\ and\ HCOO^{-} \]
The formic acid will partially dissociate in water, and it will be in equilibrium with its constituent ions. The equilibrium equation of the aqueous solution of formic acid is given as:
\[ HCOOH(aq) \leftrightharpoons H^+(aq) + HCOO^-(aq) \]
The formic acid will mostly be present in water in the form of $HCOOH$, and some parts of it will be present in water as $H^{+}$ and $HCOO^{-}$.
Numerical Result
The solutes of formic acid will be present in water as:
\[ H^+\ and\ HCOO^- \]
The equilibrium equation of formic acid in water is given as:
\[ HCOOH \leftrightharpoons H^+ + HCOO^- \]
Example
Acetic acid is a weak electrolyte. When added to water, what solutes are present in the solution? Write the equilibrium equation of the acetic acid in water.
Acetic acid is highly soluble in water, but it is a weak electrolyte. The breakdown of acetic acid into its ions does not happen to all of its molecules. Most of the molecules of acetic acid remain unchanged in their original form, and only some of the molecules break down into ions.
Acetic acid breaks down into its ions as:
\[ CH_3COOH \longrightarrow H^+ + CH_3COO^- \]
The $H^+$ ion combines with water molecules and makes hydronium ions $H_3O^+$. The anion of acetic acid is ethanoate $CH_3COO^-$ and remains in water as a negative ion.
The equilibrium equation of the acetic acid in water is given as:
\[ CH_3COOH + H_2O \leftrightharpoons H_3O^+ + CH_3COO^- \]