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

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

Step 1: Identify the Reaction Context

When a compound liberates \( \mathrm{CO}_{2} \) from \( \mathrm{NaHCO}_{3} \), it indicates an acid-base reaction. \( \mathrm{NaHCO}_{3} \) is basic, so an acidic compound is needed to release \( \mathrm{CO}_{2} \). The reaction typically involves the acidic compound donating a proton (H\(^+\)) to \( \mathrm{HCO}_{3}^{-} \), resulting in the formation of carbonic acid, which decomposes to \( \mathrm{CO}_{2} \) and water.

Step 2: Analyze the Acidity of Each Compound

Evaluate the provided options to determine their acidity or acidity potential:- (a) \( \mathrm{CH}_{3} \mathrm{NH}_{2} \) is a weak base, not an acid.- (b) \( \mathrm{CH}_{3} \mathrm{CONH}_{2} \) is a neutral amide, not acidic.- (c) \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \mathrm{Cl}^{-} \), a salt of a weak base and strong acid, acts acidic in solution.- (d) \( \left(\mathrm{CH}_{3}\right)_{4} \mathrm{~N}^{+} \mathrm{OH}^{-} \) is a strong base.

Step 3: Identify the Right Compound

From the analysis, \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \mathrm{Cl}^{-} \) is acidic in nature because it can dissociate to form \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \) and \( \mathrm{Cl}^{-} \). The \( \mathrm{CH}_{3} \mathrm{~N}^{+} \mathrm{H}_{3} \) can donate a proton (H\(^+\)) to \( \mathrm{HCO}_{3}^{-} \) of \( \mathrm{NaHCO}_{3} \), thus forming \( \mathrm{CO}_{2} \).

Key Concepts

Sodium Bicarbonate

Sodium Bicarbonate, commonly known as baking soda, is a widely used chemical compound. Its chemical formula is \( \mathrm{NaHCO}_{3} \). This compound is a mildly alkaline salt that can act as a leavening agent in baking or as an antacid to neutralize stomach acids. In its structure, it includes sodium \( \mathrm{Na}^{+} \) and bicarbonate \( \mathrm{HCO}_{3}^{-} \) ions.

When dissolved in water, Sodium Bicarbonate creates a basic solution that can interact with acidic substances in interesting ways. It is primarily the bicarbonate ion that plays a critical role during reactions with acids, leading to the release of carbon dioxide \( \mathrm{CO}_{2} \). With its ability to release gas, Sodium Bicarbonate finds utility in a myriad of applications besides cooking, such as in chemical experiments or even as a cleaning agent.

• Acts as a weak base in reactions.
• Releases \( \mathrm{CO}_{2} \) when it reacts with acid.
• Found in various everyday products.

Acidity

Acidity is a measure of how acidic a substance is. This is usually determined by the substance's ability to donate hydrogen ions \( \mathrm{H}^{+} \). In chemical reactions, acids are the compounds that donate these hydrogen ions, leading to various reaction outcomes.

In the context of the reaction between Sodium Bicarbonate and certain compounds, acidity is important because the acidic substance donates \( \mathrm{H}^{+} \) to the bicarbonate ion \( \mathrm{HCO}_{3}^{-} \). This creates carbonic acid, which is unstable and decomposes to release \( \mathrm{CO}_{2} \) gas and water.

• Acids donate hydrogen ions \( \mathrm{H}^{+} \).
• Increases hydrogen ion concentration in solutions.
• Essential for \( \mathrm{CO}_{2} \) release from Sodium Bicarbonate.

Carbon Dioxide Release

Carbon Dioxide Release in acid-base reactions involving Sodium Bicarbonate is a fascinating outcome. When an acidic compound reacts with Sodium Bicarbonate, \( \mathrm{CO}_{2} \) is generated as a result of the reaction between the acidic \( \mathrm{H}^{+} \) ions and the basic bicarbonate ions \( \mathrm{HCO}_{3}^{-} \).

The process involves the formation of carbonic acid \( \mathrm{H}_{2} \mathrm{CO}_{3} \), which is a transient intermediary. Carbonic Acid is unstable and rapidly breaks down into water \( \mathrm{H}_{2} \mathrm{O} \) and carbon dioxide, the latter escaping in the form of bubbles or fizz. This observable fizz or gas release is what makes \( \mathrm{CO}_{2} \) formation so interesting in everyday life and scientific experiments.

• Result of acid-base reaction.
• \( \mathrm{CO}_{2} \) bubbles indicate gas release.
• Widely observed in baking and experiments.