Which gas is evolved when metals react with acids to produce salts?
Answer & explanation
Correct answer: option 1
The correct answer is option 1. Hydrogen gas.
Hydrogen gas is evolved when metals react with acids to produce salts. The general chemical equation for this reaction is:
\[ \text{Metal} + \text{Acid} \rightarrow \text{Salt} + \text{Hydrogen gas} \]
For example, when zinc reacts with hydrochloric acid:
\[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \]
In this reaction, zinc chloride (ZnCl₂) is formed, and hydrogen gas (H₂) is evolved.