Hydrogen gas will reduce:

Options

A. calcium oxide
B. silver oxide
C. meagnesium oxide
D. potassium oxide

Explanation

**Step-by-Step Solution:**

1. **Understanding Reducing Agents**: A reducing agent is a substance that donates electrons to another substance, causing that substance to be reduced while the reducing agent itself is oxidized. In this case, we are looking at hydrogen gas (H₂) and its ability to act as a reducing agent.

2. **Reactivity Series**: To determine if hydrogen can act as a reducing agent, we need to refer to the reactivity series of metals. The reactivity series ranks metals from most reactive to least reactive. In this series, hydrogen is placed between metals like magnesium and silver.

3. **Identifying the Metals**: In the reactivity series, metals such as potassium, calcium, and magnesium are more reactive than hydrogen, while silver is less reactive than hydrogen. This means that hydrogen can reduce silver compounds but cannot reduce more reactive metals.

4. **Example Reaction**: Consider the reaction between hydrogen gas and silver oxide (Ag₂O). When hydrogen gas is introduced to silver oxide, it can reduce the silver ions (Ag⁺) in silver oxide to metallic silver (Ag) while itself being oxidized to water (H₂O).

5. **Chemical Equation**: The reaction can be represented as:
\[ Ag_2O + H_2 \rightarrow 2Ag + H_2O \]
In this reaction, silver oxide is reduced to silver, and hydrogen is oxidized to water.

6. **Conclusion**: Therefore, hydrogen gas can act as a reducing agent primarily for metals that are less reactive than itself, such as silver.

**Final Answer**: Hydrogen gas will reduce silver oxide (Ag₂O) to silver (Ag).

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