Problem 37 - Chemistry: An Atoms-Focused Approach

Question

Crude Oil Place the following molecules, all of which are products of the distillation of crude oil, in order in which they would appear in the distillate during simple distillation: \(\mathbf{C}_{6} \mathrm{H}_{14}, \mathrm{C}_{18} \mathrm{H}_{38}, \mathrm{C}_{12} \mathrm{H}_{26}, \mathrm{C}_{9} \mathrm{H}_{20}\)

Step-by-Step Solution

Answer

Question: Arrange the following hydrocarbon molecules in the order they would appear in the distillate during simple distillation: C\(_6\)H\(_{14}\), C\(_{18}\)H\(_{38}\), C\(_{12}\)H\(_{26}\), C\(_{9}\)H\(_{20}\). Answer: The correct order in which the molecules would appear in the distillate during simple distillation is: C\(_6\)H\(_{14}\), C\(_{9}\)H\(_{20}\), C\(_{12}\)H\(_{26}\), C\(_{18}\)H\(_{38}\).

Step 1: Understand how boiling points determine the order of distillate appearance

In simple distillation, components with lower boiling points will vaporize first and be collected earlier in the distillation process. As a general rule, smaller, lighter hydrocarbon molecules have lower boiling points, while larger, heavier hydrocarbon molecules have higher boiling points.

Step 2: Compare the molecular formulas

We have the following hydrocarbon molecules: 1. C\(_6\)H\(_{14}\) 2. C\(_{18}\)H\(_{38}\) 3. C\(_{12}\)H\(_{26}\) 4. C\(_{9}\)H\(_{20}\)

Step 3: Determine the size and weight of each molecule

We now need to determine the number of carbon atoms for each molecule, which determines its size and weight: 1. C\(_6\)H\(_{14}\) - 6 carbon atoms 2. C\(_{18}\)H\(_{38}\) - 18 carbon atoms 3. C\(_{12}\)H\(_{26}\) - 12 carbon atoms 4. C\(_{9}\)H\(_{20}\) - 9 carbon atoms

Step 4: Order the molecules based on their boiling points

Using the information from Step 3, we can now order the molecules based on their boiling points (from lowest to highest): 1. C\(_6\)H\(_{14}\) - 6 carbon atoms (smallest, lightest molecule, lowest boiling point) 2. C\(_{9}\)H\(_{20}\) - 9 carbon atoms 3. C\(_{12}\)H\(_{26}\) - 12 carbon atoms 4. C\(_{18}\)H\(_{38}\) - 18 carbon atoms (largest, heaviest molecule, highest boiling point) So, the correct order in which the molecules would appear in the distillate during simple distillation is: C\(_6\)H\(_{14}\), C\(_{9}\)H\(_{20}\), C\(_{12}\)H\(_{26}\), C\(_{18}\)H\(_{38}\).

Key Concepts

Boiling Point

The boiling point of a substance is a critical factor in distillation processes. It is the temperature at which a liquid becomes a gas. In terms of hydrocarbons, the boiling point is an indicator of molecular size and weight.
For hydrocarbons, smaller ones have lower boiling points meaning they evaporate easily and are collected first in distillation. Larger hydrocarbons exhibit higher boiling points due to stronger intermolecular forces holding the molecules together. Consequently, they require higher temperatures to vaporize. The determination of boiling points helps in organizing the order of distillation, ensuring efficient separation of different components.
For example, in the distillation of crude oil, understanding boiling points allows for the orderly collection of substances like gasoline, diesel, and others. Recognizing which hydrocarbons evaporate first can maximize efficiency in this process, which is critical in industrial and laboratory settings.

Hydrocarbons

Hydrocarbons are organic compounds consisting entirely of carbon and hydrogen atoms. They form a crucial part of crude oil distillation, existing in various forms such as alkanes, alkenes, and aromatics.
Alkanes are saturated hydrocarbons, meaning they have single bonds between carbon atoms. They have a general formula of C extsubscript{n}H extsubscript{2n+2}, an example being the molecule C extsubscript{6}H extsubscript{14}. The structure of hydrocarbons determines their physical properties, like boiling points.
In crude oil, hydrocarbons vary widely in size. Small hydrocarbons have lower boiling points and consist of fewer carbon atoms. Large hydrocarbons, having more carbon atoms, present higher boiling points. These differences enable the separation of crude oil into distinct fractions, each consisting of hydrocarbons with similar boiling points.

• Short-chain hydrocarbons: These are light and volatile, e.g., methane, ethane.
• Long-chain hydrocarbons: These are less volatile and heavier, e.g., hexadecane.

Understanding how hydrocarbons differ assists in optimizing distillation, extracting useful fuels and materials efficiently.

Crude Oil Distillation

Crude oil distillation is a fundamental process in the oil and gas industry. It involves separating crude oil into its components based on boiling points through thermal and fractional distillation.
The distillation begins by heating crude oil in a furnace, leading to vaporization of the components. Once vaporized, the mixture enters a distillation column, where it condenses at various levels based on differing boiling points.
Each level of the distillation column becomes a collection point for substances that vaporize at specific temperatures. For instance, light fractions like gasoline, collected at higher levels, have smaller molecules and lower boiling points. Heavier fractions such as lubricating oils and bitumen, with larger molecular structures, settle at the bottom.

• Fractional distillation: This is used to separate crude oil into various fuels and materials.
• Distillation columns: These structures aid in collecting hydrocarbon fractions at different levels.

This separation method maximizes the efficiency and utility of crude oil, providing an array of products such as fuels, lubricants, and raw materials for petrochemical industries.