Problem 211 - A Complete Resource Book in Chemistry for JEE Main

Question

With how many molecules of ammonia does formaldehyde condense to form urotropine?

Step-by-Step Solution

Answer

4 molecules of ammonia are required to form one molecule of urotropine.

Step 1: Understanding the Chemical Formula

Formaldehyde has the chemical formula CH₂O, while ammonia is NH₃. Urotropine, also known as hexamethylenetetramine, is (CH₂)₆N₄. This gives us an indication of how these molecules combine to form urotropine.

Step 2: Write the Reaction Equation

The balanced chemical reaction for the condensation of formaldehyde with ammonia to form urotropine is: 6 CH₂O + 4 NH₃ → (CH₂)₆N₄ + 6 H₂O. This equation shows the number of molecules of each reactant and product.

Step 3: Determine the Ratio of Reactants

The balanced equation shows that 4 molecules of ammonia react with 6 molecules of formaldehyde to form 1 molecule of urotropine. Thus, the ratio of formaldehyde to ammonia is 6:4 or 3:2.

Step 4: Calculate Molecules of Ammonia

From the balanced equation, 4 molecules of ammonia are required for each mole of urotropine formed. So, each condensation to form one molecule of urotropine requires exactly 4 molecules of ammonia.

Key Concepts

Formaldehyde

Formaldehyde, a simple and significant organic compound, has the chemical formula \( \text{CH}_2\text{O} \). It is the simplest form of aldehyde, known for its pungent smell. This compound is commonly used in industrial applications including plastic productions and as a preservative in laboratories and mortuaries.
Formally, the double-bonded oxygen gives it its particular reactivity.

• Formaldehyde is highly reactive due to its electrophilic carbon center, making it easy to engage in condensation reactions.
• Its ability to bond with various other compounds enables the formation of different polymeric products.

In the context of this particular exercise, formaldehyde acts as a reactant in the formation of hexamethylenetetramine, condensing with ammonia under the right conditions to create a new compound. This ability to easily react is what makes formaldehyde so versatile in chemical synthesis.

Ammonia

Ammonia, represented by the chemical formula \( \text{NH}_3 \), is a compound made of nitrogen and hydrogen. Known for its characteristic sharp odor, ammonia is a key player in agriculture and industrial chemistry. It is primarily used as a fertilizer due to the nitrogen it's able to provide to plants.

• As a base, ammonia can neutralize acids and is often found in household cleaners.
• Ammonia is crucial in the manufacture of plastics, explosives, and other chemicals.

During the condensation reaction depicted in the exercise, ammonia works alongside formaldehyde to produce hexamethylenetetramine. In this process, it serves as a foundation molecule, contributing to the nitrogen content of the final product. Its ability to react and form bonds makes it essential in this and many other chemical processes.

Hexamethylenetetramine

Hexamethylenetetramine, also known as urotropine, is a versatile chemical compound with the formula \( (\text{CH}_2)_6\text{N}_4 \). This compound results from the condensation of formaldehyde and ammonia. It has several applications, notably in the medical and industrial fields.
The structure of hexamethylenetetramine is a cyclic cage consisting of methylene bridges ( (\( \text{CH}_2\)) and nitrogen atoms, which gives it a stable structure.

• It is often used as a urinary antiseptic and in the treatment of urinary tract infections due to its ability to release formaldehyde in acidic conditions.
• Industrially, it is used in the production of resins and as a hardening component for rubber.

Hexamethylenetetramine showcases how simple molecules like formaldehyde and ammonia can combine to form more complex and useful products through chemical reactions.

Balanced Chemical Equation

A balanced chemical equation is fundamentally essential in chemistry to show that mass is conserved in a reaction. It ensures that the number of atoms of each element is the same on both sides of the equation.
For the reaction in this exercise:

• The balanced chemical equation is \(6\text{CH}_2\text{O} + 4\text{NH}_3 \rightarrow (\text{CH}_2)_6\text{N}_4 + 6\text{H}_2\text{O} \).
• This tells us that 6 molecules of formaldehyde react with 4 molecules of ammonia to produce 1 molecule of hexamethylenetetramine and 6 molecules of water.

Understanding balanced equations is crucial as they provide the quantitative relationships between reactants and products, guiding chemists in predicting the outcomes of reactions and scaling the processes for industrial applications. This particular reaction exemplifies how we calculate the necessary amounts of each reactant to produce the desired product without any leftover reactants.