Problem 8 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

When benzenesulfonic acid and \(p\)-nitrophenol are treated with \(\mathrm{NaHCO}_{3}\), the gases released respectively are(a) \(\mathrm{SO}_{2}, \mathrm{NO}\) (b) \(\mathrm{SO}_{2}, \mathrm{NO}_{2}\) (c) \(\mathrm{CO}_{2}, \mathrm{CO}_{2}\) (d) \(\mathrm{SO}_{2}, \mathrm{CO}_{2}\)

Step-by-Step Solution

Answer

(c) CO2, CO2

Step 1: Understanding the Reaction

Benzene sulfonic acid reacts with sodium bicarbonate ( NaHCO_{3} ), a base, in a neutralization reaction, which typically produces a salt, water, and a gas. The typical gas released due to the reaction of an acid with a bicarbonate is carbon dioxide ( CO_{2} ). Meanwhile, when NO_{2} reacts with NaHCO_{3} , it does not produce any specific observing gas like CO_{2} .

Step 2: Chemical Reactions of Components

Benzene sulfonic acid (C_{6}H_{5}SO_{3}H) with sodium bicarbonate produces sodium benzenesulfonate, water, and releases CO_{2}.\( C_6H_5SO_3H + NaHCO_3 \rightarrow C_6H_5SO_3Na + H_2O + CO_2 \)For p-nitrophenol, its acidic hydrogen can react with sodium bicarbonate, also liberating CO_{2}.\( C_6H_4(NO_2)OH + NaHCO_3 \rightarrow C_6H_4(NO_2)ONa + H_2O + CO_2 \)Thus, both benzenesulfonic acid and p-nitrophenol liberate CO_{2} upon reaction.

Step 3: Choosing the Correct Answer

Since both benzenesulfonic acid and p-nitrophenol liberate CO_{2} , we must look for an option where CO_{2} is the gas released by both compounds. Option (c) mentions the release of CO_{2} for both substances, which aligns with the chemical reactions.

Key Concepts

Benzenesulfonic Acid

Benzenesulfonic acid is an important organic compound featuring a benzene ring bonded to a sulfonic acid functional group (\( \text{SO}_3\text{H} \)). This compound is often used in chemical synthesis and industrial applications. It is known for its strong acidity, which makes it reactive with bases like sodium bicarbonate (\( \text{NaHCO}_3 \)).

In an acid-base reaction, benzenesulfonic acid provides protons to react with the bicarbonate ion. This process leads to the formation of sodium benzenesulfonate, water, and carbon dioxide gas (\( \text{CO}_2 \)).

Here's a brief look at why this happens:

• The \( \text{SO}_3\text{H} \) group is acidic, meaning it can donate a hydrogen ion.
• When it interacts with \( \text{NaHCO}_3 \), a fizzing reaction occurs, evidencing the release of \( \text{CO}_2 \) gas.
• This reaction is characteristic of acids reacting with bicarbonates: \( \text{Bicarbonate} + \text{Acid} \rightarrow \text{Salt} + \text{Water} + \text{CO}_2 \)

p-Nitrophenol

p-Nitrophenol is a chemical compound where a nitro group (\( \text{NO}_2 \)) is bonded to a phenolic compound. It is classified as a weak acid due to its hydroxyl group (\( \text{OH} \)) attached to the aromatic ring. This part of the molecule can donate hydrogen ions in reactions.

Just like benzenesulfonic acid, p-nitrophenol can react with sodium bicarbonate to produce carbon dioxide. This interaction releases \( \text{CO}_2 \) and forms a new compound, sodium p-nitrophenolate, along with water. The combination can be understood as:

• The \( \text{OH} \) group in p-nitrophenol loses a hydrogen ion (acting as an acid) when it meets bicarbonate.
• This leads to the liberation of \( \text{CO}_2 \) gas as one of the reaction's products.
• Phenolic compounds like p-nitrophenol are integral in this acid-base interaction that resembles other such neutralization reactions.

Sodium Bicarbonate

Sodium bicarbonate, commonly known as baking soda, is a versatile compound widely used in daily life and chemical reactions. It has the ability to react with various acids to produce carbon dioxide gas – a trait leveraged in both kitchen settings and scientific applications.

In the context of chemical reactions, sodium bicarbonate behaves as a mild base. When it interacts with acids like benzenesulfonic acid and p-nitrophenol, carbon dioxide gas gets released. Here's a snapshot of sodium bicarbonate's key reaction features:

• Sodium bicarbonate can release \( \text{CO}_2 \) when treated with acids (\( \text{Acid} + \text{NaHCO}_3 \rightarrow \text{Salt} + \text{H}_2\text{O} + \text{CO}_2 \)).
• Its buffering capacity allows it to stabilize pH by neutralizing acids.
• This ability makes it valuable in applications ranging from cooking and cleaning to industrial chemical processes.

By understanding sodium bicarbonate’s role in these reactions, we gain insight into its practical importance in facilitating neutralization and gas-generating reactions.