Problem 20 - Chemistry: An Atoms-Focused Approach

Question

The three most abundant gases in air are \(\mathrm{N}_{2}, \mathrm{O}_{2},\) and \(\mathrm{Ar}\). Which of them has the highest boiling point, and which has the lowest boiling point?

Step-by-Step Solution

Answer

Answer: Oxygen (O₂) has the highest boiling point, and Nitrogen (N₂) has the lowest boiling point.

Step 1: Find the boiling points for each gas

In order to determine which gas has the highest and lowest boiling points, first we need to find the boiling points of each of the three gases. The boiling points are as follows: - \(\mathrm{N}_{2}\): -195.8°C (77.36 K) - \(\mathrm{O}_{2}\): -183.0°C (90.20 K) - \(\mathrm{Ar}\): -185.8°C (87.30 K)

Step 2: Compare the boiling points

Now that we know the boiling points of each gas, let's compare them. Looking at the given boiling points, we can see that Nitrogen has the lowest boiling point (-195.8°C), followed by Argon (-185.8°C), and then Oxygen (-183.0°C) has the highest boiling point.

Step 3: Answer the question

So, with respect to the boiling points, the highest is for \(\mathrm{O}_{2}\) (Oxygen) and the lowest is for \(\mathrm{N}_{2}\) (Nitrogen).

Key Concepts

Nitrogen Boiling Point

Nitrogen, represented by the symbol \text{N}_2, has a boiling point of \(-195.8^{\circ}\text{C}\). This means it transitions from a liquid to a gas at this temperature. The boiling point reflects how much energy is required for molecules to break free from liquid to gaseous form. For nitrogen, this energy requirement is quite low compared to other gases like oxygen or argon. This low boiling point is due to weak intermolecular forces known as Van der Waals forces.

• Nitrogen makes up about 78% of Earth's atmosphere.
• Its low boiling point is advantageous for applications in cryogenics and as a coolant.

In summary, nitrogen's low boiling point reflects its role as a component of air that condenses at very low temperatures.

Oxygen Boiling Point

Oxygen, denoted as \(\text{O}_2\), boils at \(-183.0^{\circ}\text{C}\). Compared to nitrogen and argon, oxygen has the highest boiling point. This suggests that more energy is needed for oxygen molecules to transition from liquid to gas. The higher boiling point can be attributed to stronger intermolecular forces, caused by the presence of two oxygen atoms bonded together, which enhances attraction between molecules.

• Oxygen constitutes about 21% of the atmosphere.
• Its higher boiling point makes it useful in industrial processes, such as steel production.

Thus, when considering atmospheric gases, oxygen's boiling point indicates it liquefies more readily than nitrogen and argon under similar conditions.

Argon Boiling Point

Argon, with the symbol \(\text{Ar}\), has a boiling point of \(-185.8^{\circ}\text{C}\). Argon ranks between nitrogen and oxygen in terms of boiling points. This noble gas has a monatomic structure contributing to its relatively low boiling point, slightly higher than nitrogen but lower than oxygen. Intermolecular attractions in argon are primarily due to Van der Waals forces, similar to nitrogen but slightly stronger, perhaps due to its atomic mass.

• Argon makes up approximately 0.93% of the Earth's atmosphere.
• It's commonly used in welding and incandescent light bulbs to inhibit reactions with air.

Argon's boiling point showcases its stability as an inert gas, playing a vital role in processes needing a non-reactive atmosphere.