Hydrogen is preferable prepared by the reaction of

Options

A. crystal zinc with dil. HCl
B. granulated zinc with dil. HCl
C. granulated zinc with conc. HCl
D. crystal zinc with conc. HCl

Answer

To prepare hydrogen gas, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**: We need to find a suitable reaction for the laboratory preparation of hydrogen gas. A common reaction is between zinc and hydrochloric acid (HCl).

2. **Choose the Right Form of Zinc**: We will use granulated zinc instead of zinc crystals. Granulated zinc is preferred because it has a larger surface area, which allows for a faster reaction. Additionally, granulated zinc often contains copper as an impurity.

3. **Role of Copper Impurity**: The copper impurity in granulated zinc acts as a catalyst. Catalysts speed up chemical reactions without being consumed in the process. This means that the reaction between zinc and dilute HCl will occur more quickly.

4. **Write the Balanced Chemical Equation**: The reaction can be represented by the following balanced equation:
\[ \text{Zn (s)} + 2 \text{HCl (aq)} \rightarrow \text{ZnCl}_2 \text{(aq)} + \text{H}_2 \text{(g)} \]
Here, zinc reacts with hydrochloric acid to produce zinc chloride and hydrogen gas.

5. **Conclusion**: Based on the above steps, the preferable method for preparing hydrogen gas in the laboratory is by reacting granulated zinc with dilute hydrochloric acid.

### Final Answer:
The preferable preparation of hydrogen is by the reaction of **granulated zinc with dilute hydrochloric acid**.

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