At room temperature and standard pressure, chlorine gas is in which state of matter?

Analysis

The question asks for the physical state of chlorine ($Cl_2$) under standard laboratory conditions (room temperature and standard pressure).

Concept Explanation

To determine the state of matter of an element, we look at its position in the Periodic Table and its physical properties:

• Chlorine is a halogen (Group 7 element).
• Halogens exhibit a trend in their physical states as you move down the group: • Fluorine ($F_2$): Gas • Chlorine ($Cl_2$): Gas • Bromine ($Br_2$): Liquid • Iodine ($I_2$): Solid
• At room temperature (approximately 25°C) and standard pressure (1 atm), chlorine exists as a diatomic molecule ($Cl_2$). It is a pale yellow-green gas.

Step-by-Step Solution

1. Identify the substance: Chlorine is a non-metal found in Group 7 of the periodic table.
2. Recall physical properties: Chlorine is well-known in chemistry as a reactive, toxic gas used for water purification and bleaching.
3. Evaluate the options: • A (Plasma): This is an ionized state of matter, not applicable here. • B (Solid): Iodine is the solid halogen at room temperature. • C (Liquid): Bromine is the liquid halogen at room temperature. • D (Gas): Chlorine is a gas at room temperature.

Conclusion

Based on the physical properties of halogens, chlorine is a gas at room temperature and standard pressure.

Exam Tip

Remember the "Halogen State Trend": Gas, Gas, Liquid, Solid.

• Fluorine & Chlorine = Gas
• Bromine = Liquid
• Iodine = Solid (Think: "GC-LS" to remember the order down the group!)