Which test is commonly used to identify the presence of hydrogen gas in a laboratory setting?

• A. Bubble the gas through limewater; a milky appearance confirms hydrogen.
• B. Expose the gas to glowing splint; relighting confirms hydrogen.
• C. Add hydrochloric acid to the sample; effervescence confirms hydrogen.
• D. Bring a lit splint near the gas; a 'pop' sound confirms hydrogen.

Answer: (D)

Verified step by step guidance

1. Understand that hydrogen gas (H\_2) is colorless, odorless, and not easily detected by simple observation, so specific tests are used to confirm its presence.
2. Recall that bubbling a gas through limewater is a test for carbon dioxide (CO\_2), as it turns limewater milky due to the formation of calcium carbonate, so this test does not confirm hydrogen.
3. Know that exposing a gas to a glowing splint is a test for oxygen (O\_2), which will relight the splint, so this is not a test for hydrogen.
4. Recognize that adding hydrochloric acid to a sample to observe effervescence is a test for metals reacting with acid to produce hydrogen gas, but it does not directly identify hydrogen gas itself.
5. Identify that the classic and direct test for hydrogen gas is to bring a lit splint near the gas; if hydrogen is present, it will combust with a characteristic 'pop' sound, confirming its presence.