Which can be reduced to the metal by heating it in a stream of hydrogen

Options

A. Copper (II) oxide
B. Magnesium oxide
C. Aluminium oxide
D. Calcium oxide

Answer

To determine which metal oxide can be reduced to the metal by heating it in a stream of hydrogen, we need to follow these steps:

### Step 1: Understand the Concept of Reduction
Reduction refers to the process of gaining electrons or decreasing oxidation state. In the context of metal oxides, it involves converting the metal oxide back to its elemental form by removing the oxygen.

### Step 2: Identify the Reactivity of Metals
Metals can be classified based on their reactivity with hydrogen. Metals that are less reactive than hydrogen can be reduced by hydrogen gas. The metals that fall into this category include copper (Cu), mercury (Hg), silver (Ag), and gold (Au).

### Step 3: Analyze the Given Options
The options provided are:
1. Copper oxide (CuO)
2. Magnesium oxide (MgO)
3. Aluminum oxide (Al2O3)
4. Calcium oxide (CaO)

### Step 4: Determine the Reactivity of Each Metal Oxide
- **Copper Oxide (CuO)**: Copper is less reactive than hydrogen, so CuO can be reduced to copper by heating with hydrogen.
- **Magnesium Oxide (MgO)**: Magnesium is more reactive than hydrogen, so MgO cannot be reduced by hydrogen.
- **Aluminum Oxide (Al2O3)**: Aluminum is also more reactive than hydrogen, so Al2O3 cannot be reduced by hydrogen.
- **Calcium Oxide (CaO)**: Calcium is more reactive than hydrogen, so CaO cannot be reduced by hydrogen.

### Step 5: Conclusion
Among the given options, only copper oxide (CuO) can be reduced to copper metal by heating it in a stream of hydrogen.

### Final Answer
**Copper oxide (CuO)** can be reduced to the metal by heating it in a stream of hydrogen.

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