Problem 23 - Chemistry in 30 days

Question

When propionic acid is treated with aqueous sodium bicarbonate, \(\mathrm{CO}_{2}\) is liberated, The 'C" of \(\mathrm{CO}_{2}\) comes from (a) Methyl group (b) Carboxylic acid group (c) Methylene group (d) Bicarbonate

Step-by-Step Solution

Answer

The 'C' of \(\mathrm{CO}_{2}\) comes from bicarbonate.

Step 1: Identify the Reactants

The reactants in this reaction are propionic acid and aqueous sodium bicarbonate. Propionic acid has the formula \(\text{C}_2\text{H}_5\text{COOH}\), and sodium bicarbonate has the formula \(\text{NaHCO}_3\).

Step 2: Analyze the Reaction

When propionic acid reacts with sodium bicarbonate, a typical acid-base reaction occurs. The reaction can be written as: \[ \text{C}_2\text{H}_5\text{COOH} + \text{NaHCO}_3 \rightarrow \text{C}_2\text{H}_5\text{COONa} + \text{H}_2\text{O} + \text{CO}_2 \] This shows that carbon dioxide \(\text{CO}_2\) is produced.

Step 3: Determine the Source of Carbon in \(\text{CO}_2\)

In the reaction, sodium bicarbonate \(\text{NaHCO}_3\) decomposes, contributing one of its carbon atoms to form carbon dioxide (\(\text{CO}_2\)). The structure of bicarbonate showcases that it has one carbon atom, which is the source of carbon in the \(\text{CO}_2\).

Step 4: Conclude the Origin of Carbon

Considering the decomposition of bicarbonate, the carbon atom in the produced \(\text{CO}_2\) originates from the bicarbonate part of the sodium bicarbonate, not from the propionic acid itself.

Key Concepts

Propionic Acid

Propionic acid is an organic compound. It is classified as a carboxylic acid due to containing the functional group \(-\text{COOH}\). Propionic acid has the chemical formula \(\text{C}_2\text{H}_5\text{COOH}\). This structure consists of three carbon atoms, eight hydrogen atoms, and two oxygen atoms.
Carboxylic acids are known for their acidic properties, which come from the carboxyl group. In reactions, these acids can donate a proton (\(\text{H}^+\)) to another substance. This property makes it reactive with bases such as sodium bicarbonate, creating a neutralization reaction.
When mixed with sodium bicarbonate, propionic acid releases carbon dioxide as one of the products of this interaction. The knowledge of these reactions is fundamental in fields such as chemistry and biochemistry, as carboxylic acids play critical roles in biological systems and industrial processes.

Sodium Bicarbonate

Sodium bicarbonate is a common base in chemical reactions. Its chemical formula is \(\text{NaHCO}_3\). This compound is also called baking soda. It is widely known for its ability to act as a leavening agent in cooking and as an ingredient in antacids.
Sodium bicarbonate is composed of sodium (\(\text{Na}\)), hydrogen (\(\text{H}\)), carbon (\(\text{C}\)), and three oxygen (\(\text{O}_3\)). It is an amphoteric compound, meaning it can react with both acids and bases. In the presence of an acid, it undergoes a chemical reaction that releases carbon dioxide and water.

• In the reaction with propionic acid, sodium bicarbonate behaves as a base and reacts with the acidic \(-\text{COOH}\) group.
• This reaction neutralizes the acid, forms water and sodium salt, and liberates carbon dioxide gas.

Understanding sodium bicarbonate's role in acid-base reactions highlights its importance in various applications like cooking, cleaning, and medication.

Carbon Dioxide Production

Carbon dioxide (\(\text{CO}_2\)) production in reactions involving carboxylic acids and bicarbonates is a hallmark process. It symbolizes an acid-base reaction where a gas is formed.
In the reaction between propionic acid and sodium bicarbonate, carbon dioxide is a byproduct. This is because the bicarbonate ion (\(\text{HCO}_3^-\)) decomposes. It releases \(\text{CO}_2\) after acquiring a proton from the carboxyl group of propionic acid.
This process with several distinct steps includes:

• The bicarbonate ion accepts a proton, which forms carbonic acid (\(\text{H}_2\text{CO}_3\)).
• Carbonic acid is unstable. It quickly decomposes into carbon dioxide and water.
• The released carbon dioxide appears as bubbles, a sign that the reaction occurred.

This creation of \(\text{CO}_2\) is essential in educational demonstrations and real-world applications like in leavening food products or neutralizing excess stomach acid.