HCl can be prepared by

Options

A. `NaCl+ H_(2)SO_(4)overset(420 K)rarr`
B. `NaHSO_(4) + NaCl overset(820 K)rarr`
C. `NaNO_(3) + H_(2)SO_(4)`
D. both (a) and (b).

Explanation

To prepare hydrochloric acid (HCl), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The primary reactants for the preparation of HCl are sodium chloride (NaCl) and concentrated sulfuric acid (H2SO4).

2. **First Reaction**: Mix sodium chloride with concentrated sulfuric acid. This reaction occurs at a temperature of around 420 Kelvin. The reaction can be represented as:
\[ \text{NaCl} + \text{H}_2\text{SO}_4 \rightarrow \text{NaHSO}_4 + \text{HCl} \]
Here, sodium bisulfate (NaHSO4) is formed along with hydrogen chloride gas (HCl).

3. **By-product Handling**: The sodium bisulfate produced is insoluble in water, so it cannot be used directly. Therefore, we need to further process it.

4. **Second Reaction**: To obtain more HCl, we can react the sodium bisulfate with more sodium chloride at a higher temperature (820 Kelvin):
\[ \text{NaHSO}_4 + \text{NaCl} \rightarrow \text{Na}_2\text{SO}_4 + \text{HCl} \]
This reaction produces sodium sulfate (Na2SO4) and additional hydrogen chloride gas (HCl).

5. **Drying the HCl Gas**: The HCl gas produced can be dried. It is important to note that HCl should not be dried using phosphorus pentoxide or quicklime, as it reacts with these substances. Instead, concentrated sulfuric acid is used for drying.

6. **Conclusion**: Thus, HCl can be prepared by the reactions of sodium chloride with concentrated sulfuric acid, first at 420 Kelvin and then at 820 Kelvin, leading to the production of HCl gas.

### Final Answer:
HCl can be prepared by reacting sodium chloride (NaCl) with concentrated sulfuric acid (H2SO4) at two different temperatures (420 K and 820 K).

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