Calculate The Mass of N in 0.75g If Caffeine

Caffeine (C₈H₁₀N₄O₂) is a common stimulant found in coffee, tea, and energy drinks. Calculating the mass of nitrogen (N) in a given mass of caffeine is a common stoichiometry problem. This guide explains how to perform this calculation and interpret the results.

Introduction

Caffeine is a purine alkaloid with the molecular formula C₈H₁₀N₄O₂. To determine the mass of nitrogen in a sample of caffeine, we need to use stoichiometry, which relates the mass of one element to another in a compound.

The calculation involves determining the molar mass of caffeine and then using the given mass of caffeine to find the mass of nitrogen. This is a fundamental concept in chemistry that applies to many similar problems.

Formula

The mass of nitrogen (N) in a sample of caffeine can be calculated using the following formula:

mass of N = (mass of caffeine × (molar mass of N / molar mass of caffeine)) × (number of N atoms in caffeine)

Where:

mass of caffeine is the given mass (0.75g in this case)
molar mass of N is 14.007 g/mol
molar mass of caffeine is 194.19 g/mol
number of N atoms in caffeine is 4

Example Calculation

Let's calculate the mass of nitrogen in 0.75g of caffeine:

mass of N = (0.75g × (14.007 g/mol / 194.19 g/mol)) × 4

First, calculate the fraction of nitrogen in caffeine:

14.007 / 194.19 ≈ 0.0721

Then multiply by the mass of caffeine and the number of nitrogen atoms:

0.75 × 0.0721 × 4 ≈ 0.2163 g

So, 0.75g of caffeine contains approximately 0.2163g of nitrogen.

Interpreting Results

The result shows that nitrogen constitutes about 21.63% of the mass of caffeine. This is a significant portion of the compound's mass, reflecting the important role nitrogen plays in the caffeine molecule.

Understanding this calculation helps in various applications, including:

Analyzing the nutritional content of beverages
Understanding the chemical composition of stimulants
Performing similar stoichiometric calculations for other compounds

FAQ

What is the molar mass of caffeine?: The molar mass of caffeine (C₈H₁₀N₄O₂) is approximately 194.19 g/mol.
How many nitrogen atoms are in caffeine?: Caffeine contains 4 nitrogen atoms.
Can I use this calculation for other compounds?: Yes, the same method can be applied to calculate the mass of any element in any compound by knowing the compound's formula and molar mass.
Is the percentage of nitrogen in caffeine consistent?: Yes, the percentage of nitrogen in caffeine is consistent because the molar mass and formula are fixed.