Question

which of these is the most reliable way to see if a new gas has formed?
fill up a balloon
flame test
measure temperature
look at it
how does hydrogen react in a flame test?
your answer

Explanation:

• Flame test: Different gases have distinct combustion or reaction characteristics in a flame. For example, hydrogen gas (\(H_2\)) reacts explosively with oxygen (\(O_2\)) in a flame test, producing a 'pop' sound. This is a chemical reaction - \(2H_2+O_2

ightarrow 2H_2O\).

• Fill up a balloon: Just filling a balloon doesn't confirm a new gas. Air (a mixture of existing gases like \(N_2\), \(O_2\)) can fill a balloon.
• Measure temperature: Temperature change can occur in physical processes (e.g., heating water) without gas formation.
• Look at it: Gases are often colorless and odorless (e.g., \(O_2\), \(N_2\)), so visual inspection is not reliable.

For hydrogen in a flame test, the reaction is \(2H_2 + O_2\xrightarrow{\text{flame}}2H_2O\). Hydrogen reacts explosively with oxygen in the air. When a flame (a source of ignition) is brought near hydrogen gas, it burns with a 'pop' sound.

Answer:

• First question: Flame test
• Second question: Hydrogen reacts explosively with oxygen in a flame test, usually producing a 'pop' sound as it burns to form water (\(2H_2+O_2

ightarrow 2H_2O\)).