Problem 66 - Chemistry The Molecular Science

Question

The noncyclic hydrocarbon eicosane has 20 carbon atoms in each molecule. How many hydrogen atoms are in each molecule?

Step-by-Step Solution

Answer

Eicosane has 42 hydrogen atoms.

Step 1: Introduction: Understanding Eicosane

Eicosane is a member of the alkane family, which is a group of hydrocarbons made up entirely of carbon (C) and hydrogen (H) atoms. Alkanes follow the general molecular formula, which will be essential for solving the problem.

Step 1: Identify the Formula for Alkanes

The general molecular formula for alkanes is given by \( C_nH_{2n+2} \), where \( n \) is the number of carbon atoms. This formula allows you to determine the number of hydrogen atoms based on the number of carbon atoms.

Step 2: Apply the Formula to Eicosane

For eicosane, you are told there are 20 carbon atoms, so \( n = 20 \). Substitute \( n = 20 \) into the formula \( C_nH_{2n+2} \) to find the number of hydrogen atoms.

Step 3: Calculate the Number of Hydrogen Atoms

Using the formula \( C_{20}H_{2(20)+2} \), calculate the number of hydrogen atoms: \[ H = 2(20) + 2 = 40 + 2 = 42 \]. Therefore, eicosane has 42 hydrogen atoms.

Key Concepts

Eicosane

Eicosane is a fascinating molecule. It belongs to the alkane family, characterized by a linear, straight-chain of carbon atoms. This family of hydrocarbons is saturated, meaning all the carbon-carbon bonds and carbon-hydrogen bonds are single bonds. In these molecules, there is no room for additional bonding without breaking an existing bond.

• It contains 20 carbon atoms, as its name implies, because the prefix 'eicosa-' is derived from Greek, meaning twenty.
• Eicosane is part of a larger category known as higher alkanes or paraffins.
• Due to their structure, higher alkanes like eicosane are solid at room temperature.

It is important in several industrial applications, especially in the production of paraffin waxes. These waxes are widely used for coatings on food products and in making candles. Understanding molecules like eicosane helps in appreciating their structural significance in everyday products.

Molecular Formula of Alkanes

The molecular formula of alkanes is integral to identifying the structure of hydrocarbons. Alkanes follow a simple rule set by their general formula, which is written as \( C_nH_{2n+2} \). This formula tells us several things:

• The letter 'C' represents carbon atoms, while 'H' represents hydrogen atoms.
• The subscript 'n' is the number of carbon atoms present in the molecule.
• The term \( 2n+2 \) indicates the number of hydrogen atoms, as there are always two additional hydrogen atoms compared to twice the number of carbon atoms.

By applying this formula, you can reliably predict the molecular structure of any alkane. For example, knowing that eicosane has 20 carbon atoms, substituting \( n = 20 \) into the formula gives \( C_{20}H_{42} \), revealing there are 42 hydrogen atoms.This formula ensures you can determine the molecular structure of any straight-chain alkane, allowing for easy categorization and analysis of complex hydrocarbons. It provides a systematic way to study and understand these molecules based on the number of carbon atoms they contain.

Hydrocarbon Chemistry

Hydrocarbons are fundamental components of organic chemistry and are divided into several classes, including alkanes, alkenes, and alkynes. Alkanes are the simplest type, known as saturated hydrocarbons. The importance of hydrocarbons stems from their prevalence and utility in daily life. They form the basis of countless chemical processes and products:

• Many fuels, such as gasoline, diesel, and natural gas, are composed of hydrocarbon molecules.
• They are the building blocks for the petrochemical industry, producing plastics and synthetic fibers.
• Understanding hydrocarbons assists in exploring concepts like combustion, energy generation, and environmental impact.

Hydrocarbons are all about carbon and hydrogen bonding in various structures, which include chains, rings, or branched formations. The versatility of these structures underpins their use across a wide range of applications. By mastering hydrocarbon chemistry, one gains insight into both their chemical nature and practical usage, paving the way for advancements in materials science and energy solutions.