Ch.10 - Gases

Brown - Chemistry: The Central Science 14th Edition

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Brown 14th Edition

Ch.10 - Gases

Problem 14c

Chapter 10, Problem 14c

(c) Which is most likely to be a gas at room temperature and ordinary atmospheric pressure, F₂, Br₂, K₂O?

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Identify the types of substances: \( \text{F}_2 \) and \( \text{Br}_2 \) are diatomic molecules, while \( \text{K}_2\text{O} \) is an ionic compound.

Consider the physical states of diatomic molecules: \( \text{F}_2 \) is a halogen gas, \( \text{Br}_2 \) is a liquid at room temperature, and \( \text{K}_2\text{O} \) is a solid.

Recall the general trend for halogens: As you move down the group in the periodic table, the boiling points increase, making \( \text{F}_2 \) more likely to be a gas than \( \text{Br}_2 \).

Consider the nature of ionic compounds: \( \text{K}_2\text{O} \) is an ionic compound, which typically exists as a solid at room temperature due to strong ionic bonds.

Conclude that \( \text{F}_2 \), being a diatomic molecule with a low boiling point, is most likely to be a gas at room temperature and ordinary atmospheric pressure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

States of Matter

The states of matter—solid, liquid, and gas—are determined by the arrangement and energy of particles. Gases have particles that are far apart and move freely, while solids have closely packed particles that vibrate in place. Understanding these states helps predict which substances will be gaseous at room temperature and pressure.

Molecular Weight and Intermolecular Forces

Molecular weight influences the physical state of a substance. Generally, lighter molecules with weaker intermolecular forces are more likely to be gases at room temperature. For example, fluorine (F2) is a diatomic molecule with a low molecular weight, making it more likely to exist as a gas compared to heavier molecules like bromine (Br2).

Phase Diagrams

Phase diagrams illustrate the states of a substance under varying temperature and pressure conditions. They help determine the phase (solid, liquid, or gas) of a substance at specific conditions. By analyzing the phase behavior of F2, Br2, and K2O, one can predict which is most likely to be a gas at room temperature and ordinary atmospheric pressure.

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Textbook Question

A person weighing 75 kg is standing on a threelegged stool. The stool momentarily tilts so that the entire weight is on one foot. If the contact area of each foot is 5.0 cm², calculate the pressure exerted on the underlying surface in (b) atmospheres

Textbook Question

A person weighing 75 kg is standing on a threelegged stool. The stool momentarily tilts so that the entire weight is on one foot. If the contact area of each foot is 5.0 cm2, calculate the pressure exerted on the underlying surface in (a) bars

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Textbook Question

The graph below shows the change in pressure as the temperature increases for a 1-mol sample of a gas confined to a 1-L container. The four plots correspond to an ideal gas and three real gases: CO2, N2, and Cl2. (b) Use the van der Waals constants in Table 10.3 to match the labels in the plot (A, B, and C) with the respective gases 1CO2, N2, and Cl22.

(b) Which units are appropriate for expressing atmospheric pressures, N, Pa, atm, kg/m²?

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(c) Which is most likely to be a gas at room temperature and ordinary atmospheric pressure, F2, Br2, K2O?

Verified video answer for a similar problem:

Key Concepts

States of Matter

Molecular Weight and Intermolecular Forces

Phase Diagrams

(c) Which is most likely to be a gas at room temperature and ordinary atmospheric pressure, F₂, Br₂, K₂O?