Suppose you have two colorless molecular liquids, one boiling at −84°C, the other at 34°C, and both at atmospheric pressure. Which of the following statements are true? d. The two liquids have identical vapor pressures at their normal boiling points.

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Understand the concept of boiling point: The boiling point of a liquid is the temperature at which its vapor pressure equals the external atmospheric pressure.

Recognize that the boiling points provided are the temperatures where each liquid's vapor pressure equals the atmospheric pressure.

Identify that the boiling points of the two liquids are different, which implies that the temperatures at which their vapor pressures reach atmospheric pressure are different.

Conclude that if the temperatures at which their vapor pressures equal the atmospheric pressure are different, then their vapor pressures are not identical at these temperatures.

Understand that the statement 'The two liquids have identical vapor pressures at their normal boiling points' is false because their vapor pressures reach the atmospheric pressure at different temperatures.

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Key Concepts

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

Boiling Point

The boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure surrounding it. At this point, the liquid transitions to a gas. The boiling point can vary significantly between different substances due to differences in intermolecular forces, such as hydrogen bonding, dipole-dipole interactions, and London dispersion forces.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid form at a given temperature. It reflects the tendency of particles to escape from the liquid phase into the gas phase. A liquid with a higher vapor pressure at a given temperature will evaporate more readily than one with a lower vapor pressure, influencing its boiling point.

Normal Boiling Point

The normal boiling point of a substance is defined as the temperature at which it boils under standard atmospheric pressure (1 atm). At this temperature, the vapor pressure of the liquid equals the atmospheric pressure, allowing the liquid to transition to gas. Different substances have different normal boiling points based on their molecular structure and intermolecular forces.

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