Preparation Of Dihydrogen

Step 1: Understanding the Concept:
Laboratory preparation of H2 typically involves reaction of a metal with dilute acid (e.g., Zn/HCl or Fe/HCl).

Step 2: Detailed Explanation:
(A) and (D): Require high temperature, not lab-friendly.
(B) and (E): Violent reaction, not safe for lab prep.
(C): Iron reacts with dilute HCl at room temperature to produce hydrogen gas steadily.

Step 3: Final Answer:
The common lab method is Fe + 2HCl -> FeCl2 + H2.

Concept:
• Metals reacting with acids produce hydrogen gas

Step 1: Check metals
Zn and Mg react safely with dilute acids

Step 2: Reject others
Na, Ca, Ba → too reactive (dangerous) Final Conclusion:
Option (D)

Step 1: Understanding the Concept:
In the laboratory, dihydrogen ( ) gas is typically prepared by reacting an active metal with a dilute mineral acid or an aqueous alkali.
Step 2: Key Formula or Approach:
The approach is to identify the standard metal utilized in school and research laboratories for safely and efficiently generating hydrogen gas.
Step 3: Detailed Explanation:
The most common and standard method for preparing dihydrogen in the laboratory involves the reaction of granulated zinc with dilute hydrochloric acid ( ) or dilute sulfuric acid ( ).
The chemical reaction is:
Granulated zinc is preferred over pure block zinc because the impurities present in it act as a local catalyst (forming micro-galvanic cells) which speeds up the reaction.
Alternatively, zinc can also react with aqueous alkali (like NaOH) to produce hydrogen and sodium zincate, though acid is more commonly used.
Highly reactive metals like Sodium or Potassium are not used in the lab because their reaction with acids or water is violently explosive.
Step 4: Final Answer:
Granulated Zinc is the metal used.