Which of the following best describes what happens when Br_2(l) boils at its normal boiling point?

• A. Br_2(l) undergoes a chemical reaction to form Br_2(g).
• B. Br_2(l) freezes to form solid bromine.
• C. The temperature of Br_2(l) decreases rapidly.
• D. The vapor pressure of Br_2(l) equals atmospheric pressure.

Answer: (D)

Verified step by step guidance

1. Understand that boiling is a physical change where a liquid turns into a gas when its vapor pressure equals the external (atmospheric) pressure.
2. Recall that vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature.
3. At the normal boiling point, the vapor pressure of the liquid equals the atmospheric pressure, allowing bubbles of vapor to form within the liquid.
4. Recognize that boiling does not involve a chemical reaction; the substance remains chemically the same, just changing phase from liquid to gas.
5. Therefore, the correct description is that the vapor pressure of Br_2(l) equals atmospheric pressure at its normal boiling point.