In which reactions hydrogen is acting as an oxidizing agent?

Options

A. with iodine to give hydrogen iodide
B. with lithium to give lithium hydride
C. with nitrogen to give ammonia
D. with sulphur to give hydrogen sulphide

Answer

To determine in which reactions hydrogen acts as an oxidizing agent, we need to analyze the oxidation states of the elements involved in the reactions. Let's break down the steps to find the answer.

### Step-by-Step Solution:

1. **Identify the Reactions**: We need to evaluate the reactions provided in the options and identify the one where hydrogen is involved.

2. **Analyze the Reaction**: Let's take the second option as mentioned in the video transcript:
- The reaction is:
\[ \text{Li} + \text{H}_2 \rightarrow \text{LiH} \]
- Here, lithium (Li) reacts with hydrogen (H₂) to form lithium hydride (LiH).

3. **Determine Oxidation States**:
- In elemental form, both lithium and hydrogen have an oxidation state of 0.
- In lithium hydride (LiH), the oxidation states are:
- Lithium (Li) = +1
- Hydrogen (H) = -1

4. **Identify Changes in Oxidation States**:
- Lithium changes from 0 to +1 (oxidation).
- Hydrogen changes from 0 to -1 (reduction).

5. **Determine the Role of Hydrogen**:
- Since lithium is oxidized (loses electrons) and hydrogen is reduced (gains electrons), hydrogen is acting as an oxidizing agent because it causes the oxidation of lithium.

6. **Conclusion**: Therefore, in this reaction, hydrogen acts as an oxidizing agent.

### Final Answer:
In the reaction where lithium reacts with hydrogen to produce lithium hydride, hydrogen acts as an oxidizing agent.

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