Problem 48 - A Complete Resource Book in Chemistry for JEE Main

Question

Which compound will liberate \(\mathrm{CO}_{2}\) from \(\mathrm{NaHCO}_{3}\) solution? (a) \(\mathrm{CH}_{3} \mathrm{NH}_{2}\) (b) \(\mathrm{CH}_{3} \mathrm{CONH}_{2}\) (c) \(\mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \mathrm{Cl}^{-}\) (d) \(\left(\mathrm{CH}_{3}\right)_{4} \mathrm{~N}^{+} \mathrm{OH}^{-}\)

Step-by-Step Solution

Answer

Compound (c) \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \mathrm{Cl}^{-} \) will liberate \( \mathrm{CO}_{2} \) from \( \mathrm{NaHCO}_{3} \).

Step 1: Identify the Reaction and Requirement

In order to liberate carbon dioxide (\( \mathrm{CO}_{2} \)) from \( \mathrm{NaHCO}_{3} \), the compound must react with \( \mathrm{NaHCO}_{3} \) in such a way that \( \mathrm{CO}_{2} \) gas is released. This typically requires an acid or a substance that can produce an acidic environment.

Step 2: Analyze Each Compound

Let's analyze each option to see which can create an acidic environment:- (a) \( \mathrm{CH}_{3} \mathrm{NH}_{2} \) is a weak base and will not provide an acidic environment.- (b) \( \mathrm{CH}_{3} \mathrm{CONH}_{2} \) is neutral and will not significantly affect the pH of the solution.- (c) \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \mathrm{Cl}^{-} \) contains \( \mathrm{NH}_{4}^{+} \) which can release \( \mathrm{H}^{+} \) ions, providing an acidic environment.- (d) \( \left(\mathrm{CH}_{3}\right)_{4} \mathrm{~N}^{+} \mathrm{OH}^{-} \) is a strong base and increases pH, not suitable for liberating \( \mathrm{CO}_{2} \).

Step 3: Select Potential Compound

From Step 2, we see that only option (c), \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \mathrm{Cl}^{-} \), which can dissociate to \( \mathrm{NH}_{4}^{+} \), can provide \( \mathrm{H}^{+} \) ions to react with \( \mathrm{NaHCO}_{3} \) to liberate \( \mathrm{CO}_{2} \).

Step 4: Confirm the Reaction

The actual reaction occurs because \( \mathrm{H}^{+} \) from \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \) reacts with \( \mathrm{HCO}_{3}^{-} \) to form \( \mathrm{H}_{2}\mathrm{O} \) and \( \mathrm{CO}_{2} \). Formula of the reaction:\[ \mathrm{H}^{+} + \mathrm{NaHCO}_{3} \rightarrow \mathrm{Na}^{+} + \mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O} \]

Key Concepts

Acid-Base Reactions

Acid-base reactions are chemical processes where acids and bases interact in solution. This interaction can lead to the exchange of hydrogen ions (709). In the context of the exercise, an acidic compound is one that can donate hydrogen ions to a base. Bases, on the other hand, can accept these hydrogen ions. When an acid reacts with a base, they often neutralize each other, forming water and, in some cases, releasing gases such as carbon dioxide (6c0).

• An example of an acid is hydrochloric acid (HCl), which dissociates in water to release hydrogen ions.
• A typical base example is sodium hydroxide (4c1), which dissociates to give hydroxide ions (707).

In our initial problem, to liberate 6c0 from 5f5, the compound used has to effectively donate protons to react with bicarbonate ions.

Carbon Dioxide Liberation

Carbon dioxide liberation refers to the process through which 6c0 gas is released from a chemical reaction. In a laboratory setting, this is often demonstrated by the reaction of acids with carbonates or bicarbonates.

• The reaction between an acid (such as acetic acid) and bicarbonate (like sodium bicarbonate) results in the formation of carbon dioxide gas, water (4a7), and a corresponding salt (90c2).

For example, when hydrogen ions (709) combine with bicarbonate (5f5), they form carbonic acid (94c) which quickly decomposes into water and carbon dioxide, leading to bubbling in the solution as the gas is released.

pH and Acidity

pH is a scale used to specify the acidity or basicity of an aqueous solution. It ranges typically from 0 (very acidic) to 14 (very basic), with 7 being neutral. The pH of a solution influences its chemical properties, determining whether it can participate in acid-base reactions effectively.

• An acidic solution has a low pH, meaning a high concentration of hydrogen ions (709).
• On the contrary, a basic solution features a high pH, indicating a higher concentration of hydroxide ions (707).

When selecting a compound to react with 5f5, the effectiveness relies on its ability to lower the pH enough to liberate 6c0.

Ammonium Salts

Ammonium salts, such as 93c3, are compounds containing the ammonium ion (709) paired with a negative ion like chloride (90c8). They are significant in chemical reactions because they can act as a source of hydrogen ions, contributing to the acidity of solutions.

• Ammonium ions can donate hydrogen ions, making the surrounding environment more acidic.
• This ability is why certain ammonium salts can participate in reactions that liberate 6c0 by donating protons to bicarbonate ions.

In acid-base reactions, ammonium ions dissociate and release hydrogen ions, which can then react with bicarbonate to produce 6c0 and water.

Organic Chemistry

Organic chemistry is the study of carbon-based compounds and their reactions. This field encompasses a variety of compounds, including those mentioned in the exercise, like amines and amides.

• Methylamine (708) is an organic compound behaving as a weak base, with its amino group (90e0) able to accept protons.
• Methylammonium chloride is an example of an ammonium salt in organic chemistry and can affect the pH due to its ammonium group (93c3).

When it comes to reactions with bicarbonate, particular organic compounds can significantly influence whether a reaction will result in 6c0 gas being released.