Question

Which gas is usually evolved when an acid reacts with a metal? How will you test the presence of this gas?

Hint:

Remember: Carbon dioxide extinguishes fire (turns limewater milky), Oxygen supports vigorous burning, Hydrogen burns with a pop.

Answer 1

Step 1: Understanding the Concept:
Active metals displace hydrogen from dilute acids.

Step 2: Detailed Explanation:
When an active metal (like Zinc or Magnesium) reacts with a dilute acid (like \(\text{HCl}\) or \(\text{H}_2\text{SO}_4\)), it forms a metal salt and liberates Hydrogen gas.
Reaction example: \(\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow\).
Test for Hydrogen gas:
Bring a burning splinter or matchstick near the mouth of the test tube where the gas is evolving.
If the gas burns with a characteristic 'pop' sound, it confirms the presence of Hydrogen gas.

Step 3: Final Answer:
Hydrogen gas is evolved, and it is tested by observing a 'pop' sound with a burning splinter.