In which of the following compound does hydrogen exhibit a negative oxidation state:

Options

A. `LiH`
B. `H_(2)O`
C. `HCl`
D. none of these

Explanation

To determine in which of the given compounds hydrogen exhibits a negative oxidation state, we will calculate the oxidation state of hydrogen in each compound.

### Step-by-Step Solution:

1. **Identify the compounds**: The compounds given are LiH, H2O, and HCl.

2. **Calculate the oxidation state of hydrogen in LiH**:
- Let the oxidation state of hydrogen be \( X \).
- Lithium (Li) has a +1 oxidation state.
- The overall charge of the compound is 0.
- Therefore, we can write the equation:
\[ +1 + X = 0 \]
- Solving for \( X \):
\[ X = -1 \]
- Thus, in LiH, hydrogen exhibits a **negative oxidation state** of -1.

3. **Calculate the oxidation state of hydrogen in H2O**:
- Let the oxidation state of hydrogen be \( X \).
- There are 2 hydrogen atoms, so the contribution is \( 2X \).
- Oxygen (O) has a -2 oxidation state.
- The overall charge of the compound is 0.
- Therefore, we can write the equation:
\[ 2X - 2 = 0 \]
- Solving for \( X \):
\[ 2X = 2 \quad \Rightarrow \quad X = +1 \]
- Thus, in H2O, hydrogen exhibits a **positive oxidation state** of +1.

4. **Calculate the oxidation state of hydrogen in HCl**:
- Let the oxidation state of hydrogen be \( X \).
- Chlorine (Cl) has a -1 oxidation state.
- The overall charge of the compound is 0.
- Therefore, we can write the equation:
\[ X - 1 = 0 \]
- Solving for \( X \):
\[ X = +1 \]
- Thus, in HCl, hydrogen exhibits a **positive oxidation state** of +1.

5. **Conclusion**:
- After calculating the oxidation states, we find that hydrogen exhibits a negative oxidation state only in **LiH**.

### Final Answer:
The compound in which hydrogen exhibits a negative oxidation state is **LiH**.

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