Question

Column-I Column-II (Compound) (Statements) (A) Carboxylic acid (P) Soluble in aqueous \(\mathrm{NaHCO}_{3}\) (B) Picric acid (Q) No COOH group is present (C) Squaric acid (R) Soluble in aqueous \(\mathrm{NaOH}\) (D) Salicylic acid (S) \(-\) OH group is present

Short answer

The matched pairs for the given compounds and their properties are as follows: (A) Carboxylic acid - (P) Soluble in aqueous \(\mathrm{NaHCO}_{3}\) (B) Picric acid - (Q) No COOH group is present, (S) OH group is present (C) Squaric acid - (R) Soluble in aqueous \(\mathrm{NaOH}\) (D) Salicylic acid - (P) Soluble in aqueous \(\mathrm{NaHCO}_{3}\), (S) OH group is present

Step-by-step solution

Identify the compounds

List out all the given compounds in Column I. We have: 1. Carboxylic acid (A) 2. Picric acid (B) 3. Squaric acid (C) 4. Salicylic acid (D)

Analyze the properties of each compound

Based on our knowledge of these compounds, we will analyze their properties: (A) Carboxylic Acid: These are organic compounds that contain a carboxyl group (-COOH). They react with aqueous \(\mathrm{NaHCO}_{3}\) (sodium bicarbonate) to form water-soluble salts, which make them soluble in aqueous \(\mathrm{NaHCO}_{3}\). (B) Picric Acid: It is an organic compound with a formula \({\mathrm{C}_{6}}{\mathrm{H}_{2}}({\mathrm{NO}_{2}})_{3}\mathrm{OH}\). Because it contains 3 nitro groups and an OH group, it is a strong acid and soluble in aqueous \(\mathrm{NaOH}\). (C) Squaric Acid: This is an organic compound with the formula \(\mathrm{C}_{4}\mathrm{O}_{4}\mathrm{H}_{4}\). It contains 2 COOH groups and 2 OH groups. It is a diacid, which means it can donate two protons and is soluble in aqueous \(\mathrm{NaOH}\). (D) Salicylic Acid: It is an organic compound with the formula \(\mathrm{C}_{6}\mathrm{H}_{4}(\mathrm{OH})\mathrm{COOH}\). It contains a COOH group and an OH group. It is a weak acid and soluble in aqueous \(\mathrm{NaHCO}_{3}\).

Match the compounds with the statements in Column II

Now, using our analysis above, we will match each compound with its appropriate statement(s) from Column II: (A) Carboxylic acid - Soluble in aqueous \(\mathrm{NaHCO}_{3}\). Thus, it matches with (P). (B) Picric acid - No COOH group is present, but the OH group is present. Thus, it matches with (Q) and (S). (C) Squaric acid - Soluble in aqueous \(\mathrm{NaOH}\) due to its 2 COOH groups. Thus, it matches with (R). (D) Salicylic acid - Contains a COOH group and an OH group making it soluble in aqueous \(\mathrm{NaHCO}_{3}\). Thus, it matches with (P) and (S).

Write the final matched pairs

After matching the compounds with their appropriate statements, we can write the matched pairs as follows: (A) - (P) (B) - (Q), (S) (C) - (R) (D) - (P), (S)

Key concepts

Carboxylic Acid

Carboxylic acids are a class of organic compounds that are known for containing a carboxyl group (-COOH). This group, comprising a carbonyl ( C=O ) and a hydroxyl ( -OH ) group, is what gives the carboxylic acids their distinctive acidity.
The acidic nature of carboxylic acids allows them to donate a proton ( H^+ ) from their carboxyl group. This behavior is the primary reason behind many chemical reactions they undergo.

• Strong Hydrogen Bonds: Carboxylic acids form strong hydrogen bonds. These bonds can occur not only with water but also with themselves, leading to dimer formation.
• Acid-Base Reactions: They react with bases like sodium hydroxide (NaOH) and sodium bicarbonate ( NaHCO_3 ), forming salts.
• Presence in Nature: Carboxylic acids are widespread in nature. For example, citric acid in citrus fruits and acetic acid in vinegar.

Their solubility in aqueous NaHCO_3 solutions is due to this acidic character. When they react with NaHCO_3, carbon dioxide ( CO_2 ) is released, which is a classic indicator of this reaction.

Solubility in Sodium Bicarbonate

Solubility is a key property of acids that helps distinguish weak acids from strong acids. One way to assess the strength of an acid is by examining its solubility in sodium bicarbonate (NaHCO_3).
In a typical reaction, stronger acids or those similar in strength to carbonic acid will react vigorously with NaHCO_3. This reaction results in the formation of bubbles due to the evolution of carbon dioxide (CO_2).

• Chemical Reaction: When carboxylic acids react with sodium bicarbonate, a salt, water, and carbon dioxide are produced.This can be represented by the equation: \[ \mathrm{RCOOH + NaHCO_3 \rightarrow RCOONa + CO_2 + H_2O } \]
• Detecting Acid Strength: Observing whether an acid is soluble in sodium bicarbonate is a helpful practical approach to determine acid strength.Strong acids like HCl completely dissociate, but with weaker acids like acetic acid, you will witness the CO_2 release reaction.

The presence of bubbles or fizzing is a visual cue for students performing this reaction in lab experiments, indicating the interaction between acidic and bicarbonate ions.

Properties of Acids

Acids are chemical species known for their distinctive sour taste and ability to change litmus paper red. In organic chemistry, acids like carboxylic acids play crucial roles. Understanding their properties is key to mastering acid-base chemistry.

• Proton Donors: Acids are known as proton donors because they can donate a hydrogen ion ( H^+ ). This donation ability gives acids their characteristic property of turning blue litmus paper red.
• Dissociation: In water, acids dissociate, converting hydrogen ions into solution, which leads to low pH levels.
• Chemical Reactions: Acids often engage in reactions where they donate protons, interact with bases, and form water and salts in neutralization reactions.

Organic acids especially exhibit this acid behavior due to the presence of functional groups like COOH . Students must appreciate how the structure of these acids contributes to their reactivity and physical properties such as solubility.