A reaction produces a colorless gas, which is collected by water displacement. A glowing splint inse — States of Matter Chemistry Question

STEPS:

1. Identify the color of the gas: The problem states that the reaction produces a colorless gas. This immediately allows us to eliminate any highly colored gases or substances that are not gases at standard temperature and pressure.
2. Evaluate the gas collection method (water displacement): Collecting a gas via water displacement requires the gas to have very low solubility in water and to not chemically react with water. Highly soluble or reactive gases would dissolve in or react with the water rather than bubbling through it to fill the collection bottle. This strongly points toward nonpolar, relatively unreactive gases.
3. Analyze the glowing splint test: The clue states that a glowing splint inserted into the bottle of gas is extinguished.
* A gas that supports combustion (such as oxygen) would cause a glowing splint to reignite or burst back into a flame.
* An inert gas that does not support combustion deprives the splint of the oxygen needed to sustain the chemical reaction, causing the glowing splint to go out (be extinguished).
4. Identify the correct gas ($\text{N}_2$): Nitrogen gas ($\text{N}_2$) is a colorless, odorless, nonpolar diatomic gas with extremely low water solubility (which allows it to be collected by water displacement). Because of its exceptionally strong nitrogen-nitrogen triple bond, $\text{N}_2$ is chemically inert at room temperature and does not support combustion, meaning it will extinguish the glowing splint. This perfectly matches all criteria, confirming Option A.

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WHY_OTHERS_WRONG:

• B is incorrect: Nitrogen dioxide ($\text{NO}_2$) is a highly toxic, reddish-brown gas, which violates the colorless requirement. Furthermore, it is extremely soluble in water and reacts with it to form acidic solutions, meaning it cannot be successfully collected by water displacement.
• C is incorrect: Although oxygen ($\text{O}_2$) is a colorless gas that can be collected via water displacement, it actively supports combustion. Inserting a glowing splint into a bottle of $\text{O}_2$ would cause the splint to reignite rather than extinguish.
• D is incorrect: Bromine ($\text{Br}_2$) is a heavy, reddish-brown liquid at room temperature that produces a highly colored, corrosive red-brown vapor, violating the "colorless gas" criteria.
• E is incorrect: Chlorine ($\text{Cl}_2$) is a pale yellow-green gas with a sharp, suffocating odor, meaning it is not colorless. Additionally, chlorine gas reacts with and dissolves in water, making water displacement an inappropriate collection method.