Animated Solution for Chemistry - Basic Concepts in Chemistry: The mass percentage of nitrogen in histamine is ………

Imagine your eyes watering, your nose running, and your skin itching during allergy season. The microscopic culprit behind all this chaos? A tiny, nitrogen-packed molecule called histamine.

In this problem, we are tasked with finding exactly how much of this molecule's weight is made up of pure nitrogen. It is a classic stoichiometric exercise that bridges the gap between a biological structure and mathematical reality.

Before we can calculate anything, we need to know what we are dealing with. Histamine is a biologically active amine. If you look at its skeletal structure, you will notice two distinct parts: a five-membered imidazole ring and a short ethylamine chain attached to it.

To find the mass percentage, we first need the molecular formula. By carefully counting the atoms in the structure, we find: - 5 Carbon atoms (3 forming the backbone of the ring, 2 in the side chain). - 9 Hydrogen atoms (distributed across the carbons and nitrogens). - 3 Nitrogen atoms (2 locked inside the aromatic ring, and 1 at the very end of the chain).

This gives us the molecular formula: $C_5{H}_9{N}_3$.

Now that we have the formula, we need to determine the total molar mass of the compound. We do this by summing the atomic masses of all constituent atoms:

So, one mole of histamine weighs exactly $111\text{ g}$.

Our goal is to find the mass percentage of nitrogen. The formula for mass percentage is beautifully intuitive:

We already know that there are 3 nitrogen atoms, each contributing $14\text{ g/mol}$. Therefore, the total mass of nitrogen in one mole is:

Now, we simply substitute our raw values into the percentage formula:

Executing the division gives us $37.8378...\%$. Rounding this off to two decimal places, we arrive at our final, elegant answer: $37.84\%$.

Think about that for a second—nearly $38\%$ of histamine's entire mass is just nitrogen! This incredibly high nitrogen density is exactly what makes histamine a strong biological base, allowing it to bind so effectively to the receptors in your body and trigger those intense allergic responses.