Hydrogen is not obtained when sodium reacts with

Options

A. Cold water
B. Dilute `H_(2)SO_(4)`
C. Molten NaCl
D. Dilute HCl

Answer

To solve the question "Hydrogen is not obtained when sodium reacts with," we need to analyze the reactions of sodium with different substances.

### Step-by-Step Solution:

1. **Identify the Reactants**: The question asks about the reactions of sodium with various substances. We will consider the following options:
- Cold water
- Dilute H2SO4 (sulfuric acid)
- Molten NaCl (sodium chloride)
- Dilute HCl (hydrochloric acid)

2. **Reaction of Sodium with Cold Water**:
- When sodium reacts with cold water, it produces sodium hydroxide (NaOH) and hydrogen gas (H2).
- Reaction:
\[ 2 \text{Na} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2 \]
- **Conclusion**: Hydrogen is obtained.

3. **Reaction of Sodium with Dilute H2SO4**:
- Sodium reacts with dilute sulfuric acid to produce sodium sulfate and hydrogen gas.
- Reaction:
\[ 2 \text{Na} + \text{H}_2\text{SO}_4 \rightarrow \text{Na}_2\text{SO}_4 + \text{H}_2 \]
- **Conclusion**: Hydrogen is obtained.

4. **Reaction of Sodium with Molten NaCl**:
- When sodium reacts with molten sodium chloride, there is no hydrogen present in the reactants, and thus, no hydrogen can be produced.
- Reaction:
\[ \text{Na} + \text{NaCl} \rightarrow \text{Na}_2 + \text{Cl}_2 \]
- **Conclusion**: Hydrogen is NOT obtained.

5. **Reaction of Sodium with Dilute HCl**:
- Sodium reacts with dilute hydrochloric acid to produce sodium chloride and hydrogen gas.
- Reaction:
\[ 2 \text{Na} + 2 \text{HCl} \rightarrow 2 \text{NaCl} + \text{H}_2 \]
- **Conclusion**: Hydrogen is obtained.

### Final Answer:
The correct option is **Molten NaCl**, as hydrogen is not obtained when sodium reacts with it.