Amongst the following the total number of elements, which produce `H_2` gas with sodium hydroxide is:
Zn, Al, Sn, Pb, P , Si

Options

A. 3
B. 4
C. 5
D. 6

Explanation

To solve the question regarding which elements produce hydrogen gas (H₂) when reacting with sodium hydroxide (NaOH), we will analyze each element one by one.

### Step-by-Step Solution:

1. **Zinc (Zn)**:
- Reaction: \( \text{Zn} + 2 \text{NaOH} \rightarrow \text{Na}_2\text{ZnO}_2 + \text{H}_2 \)
- Zinc reacts with sodium hydroxide to produce sodium zincate and hydrogen gas.
- **Produces H₂**.

2. **Aluminium (Al)**:
- Reaction: \( 2 \text{Al} + 2 \text{NaOH} + 6 \text{H}_2\text{O} \rightarrow 2 \text{Na}_3\text{Al(OH)}_6 + 3 \text{H}_2 \)
- Aluminium reacts with sodium hydroxide in the presence of water to produce sodium aluminate and hydrogen gas.
- **Produces H₂**.

3. **Tin (Sn)**:
- Reaction: \( \text{Sn} + 2 \text{NaOH} + 2 \text{H}_2\text{O} \rightarrow \text{Na}_2\text{Sn(OH)}_4 + \text{H}_2 \)
- Tin reacts with sodium hydroxide and water to produce sodium stannate and hydrogen gas.
- **Produces H₂**.

4. **Lead (Pb)**:
- Reaction: \( \text{Pb} + 2 \text{NaOH} + 2 \text{H}_2\text{O} \rightarrow \text{Na}_2\text{Pb(OH)}_4 + \text{H}_2 \)
- Lead reacts with sodium hydroxide and water to produce lead hydroxide and hydrogen gas.
- **Produces H₂**.

5. **Phosphorus (P)**:
- Reaction: \( \text{P}_4 + 3 \text{NaOH} + 3 \text{H}_2\text{O} \rightarrow 3 \text{NaH}_2\text{PO}_2 + \text{PH}_3 \)
- Phosphorus reacts with sodium hydroxide to produce phosphine and sodium hypophosphite, but does not produce hydrogen gas.
- **Does NOT produce H₂**.

6. **Silicon (Si)**:
- Reaction: \( \text{Si} + 2 \text{NaOH} + 2 \text{H}_2\text{O} \rightarrow \text{Na}_2\text{SiO}_3 + \text{H}_2 \)
- Silicon reacts with sodium hydroxide and water to produce sodium silicate and hydrogen gas.
- **Produces H₂**.

### Summary:
- The elements that produce hydrogen gas when reacting with sodium hydroxide are: **Zinc (Zn)**, **Aluminium (Al)**, **Tin (Sn)**, **Lead (Pb)**, and **Silicon (Si)**.
- **Total number of elements producing H₂**: **5 elements**.

### Final Answer:
**5 elements produce H₂ gas with sodium hydroxide.**

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