Question

The compound that does NOT liberate \(\mathrm{CO}_{2}\), on treatment with aqueous sodium bicarbonate solution, is (A) Benzoic acid (B) Benzenesulphonic acid (C) Salicylíc acid (D) Carbolic acid (Phenol)

Short answer

Phenol (carbolic acid) does NOT liberate CO_2 on treatment with aqueous sodium bicarbonate solution.

Step-by-step solution

Understand the Chemical Reaction

When carboxylic acid or sulfonic acid react with sodium bicarbonate (NaHCO_3), they typically form carbon dioxide (CO_2), water (H_2O), and a salt. The reaction proceeds due to the acidic nature of these compounds, which can donate a proton to the bicarbonate ion.

Analyze the Given Options

Look at each compound to see whether it has the required acidity to react with NaHCO_3 and release CO_2. Carboxylic acids, like benzoic acid (C6H5COOH) and salicylic acid (C7H6O3), can release CO_2. Benzenesulphonic acid, being a strong acid can also react with NaHCO_3. Carbolic acid (phenol) is a very weak acid and does not react with NaHCO_3 in the same way as the others.

Identify the Compound That Does Not Release CO_2

Given the properties of the compounds listed, phenol (C6H5OH) or carbolic acid is the one that does not release CO_2 upon treatment with aqueous sodium bicarbonate because it is a weak acid and doesn't have the required acidity to decompose NaHCO_3.

Key concepts

Chemical Reactions

Chemical reactions are the processes by which substances interact to form new products with different chemical properties. One common type of chemical reaction is the reaction between acids and bases. This interaction often results in the release of gases, formation of water, and production of salts.

In the context of the exercise, the focus is on a specific chemical reaction where an acid reacts with sodium bicarbonate (NaHCO₃). When an acid donates a proton to the bicarbonate ion, carbon dioxide (CO₂), water (H₂O), and a corresponding salt are formed. This kind of reaction is an exemplary representation of an acid-base reaction demonstrating the reactivity of different chemical substances based on their acidic or basic nature.

Understanding the nuances of these reactions is crucial for students as it helps predict the outcome when different chemicals are combined. This predictability is important in both laboratory settings and real-world applications, ranging from acid rain's interaction with rocks to the baking soda's role in cooking.

Acid-Base Reactions

Acid-base reactions are fundamental to chemistry and involve the transfer of protons (H⁺) from an acid to a base. The most well-known theory to describe acids and bases is the Brønsted-Lowry theory, which defines an acid as a substance that can donate a proton, and a base as a substance that can accept a proton.

In the exercise's scenario, sodium bicarbonate acts as a base and accepts a proton from carboxylic or sulfonic acids. This results in the release of carbon dioxide gas, a clear indication of such a reaction taking place. To fully grasp the concept, students need to recognize the strength of the acid involved, as not all acids react with sodium bicarbonate with enough vigor to release CO₂ visibly. For instance, phenol (also known as carbolic acid) is not acidic enough to decompose sodium bicarbonate; hence, no CO₂ is liberated.

By exploring the acid-base reactivity, students can better understand the properties of various compounds and predict the outcomes of mixing them, a skill that is invaluable in experimental chemistry and many industrial processes.

Carboxylic Acids

Carboxylic acids are a class of organic compounds characterized by the presence of a carboxyl group (-COOH). This group consists of a carbon double-bonded to an oxygen and single-bonded to a hydroxyl group (-OH). Carboxylic acids are well-known for being more acidic than alcohols and phenols due to the resonance stabilization of their anions, as well as the electron-withdrawing effect of the double-bonded oxygen.

In reactions with sodium bicarbonate, carboxylic acids easily donate a proton, which is taken by the bicarbonate to form CO₂, water, and a carboxylate salt. This reaction is typically used as a qualitative test to determine the presence of carboxylic acids in a substance. This characteristic reaction is key to identifying compounds like benzoic and salicylic acids in the provided exercise.

Understanding carboxylic acids' properties and their reactions with bases broadens a student's ability to engage with organic chemistry and to appreciate the widespread occurrence of these compounds in pharmaceuticals, manufacturing, and even in our daily lives as vinegar (acetic acid).