When ____ is passed over red hot iron, oxide of iron and hydrogen are produced.

Explanation

To solve the question, we need to identify the substance that is passed over red hot iron to produce iron oxide and hydrogen.

### Step-by-Step Solution:

1. **Identify the Reactants**: The question states that something is passed over red hot iron (Fe). We need to determine what this substance is.

2. **Recognize the Context**: In chemistry, when iron is heated, it can react with certain gases. One common reaction involves steam (H₂O).

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