How `H_(2)S` is liberated in laboratory

Options

A. `FeSO_(4)+H_(2)SO_(4)`
B. `FeS+dil. H_(2)SO_(S)`
C. `FeS+conc.H_(2)SO_(4)`
D. `"Elementary H"_(2)+"elementary S"`

Explanation

To liberate hydrogen sulfide gas (H₂S) in a laboratory setting, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The primary reactant we will use is iron(II) sulfide (FeS). We will also need a dilute acid, specifically dilute sulfuric acid (H₂SO₄).

2. **Set Up the Reaction**: In a laboratory setup, take a small amount of iron(II) sulfide (FeS) and place it in a reaction flask or beaker.

3. **Add Dilute Sulfuric Acid**: Slowly add dilute sulfuric acid (H₂SO₄) to the flask containing FeS. It is important to add the acid gradually to control the reaction.

4. **Observe the Reaction**: As the dilute sulfuric acid reacts with iron(II) sulfide, you will observe the evolution of gas. The reaction can be represented by the following chemical equation:
\[ \text{FeS (s)} + \text{H}_2\text{SO}_4 \text{(aq)} \rightarrow \text{FeSO}_4 \text{(aq)} + \text{H}_2\text{S (g)} \]
This indicates that iron(II) sulfate (FeSO₄) is formed along with hydrogen sulfide gas (H₂S).

5. **Collect the Gas**: The hydrogen sulfide gas produced can be collected by using an inverted test tube or a gas jar placed over the reaction flask, allowing the gas to displace the air.

6. **Safety Precautions**: Ensure that you are working in a well-ventilated area or under a fume hood, as H₂S is a toxic gas with a characteristic rotten egg smell.

### Final Reaction Summary:
The overall reaction for the liberation of H₂S in the laboratory is:
\[ \text{FeS (s)} + \text{H}_2\text{SO}_4 \text{(dilute)} \rightarrow \text{FeSO}_4 \text{(aq)} + \text{H}_2\text{S (g)} \]