When metal reacts with O2 it forms black solid which on reacting with Hydrogen gives back metal. Identify metal.

Explanation

To solve the problem step by step, let's analyze the information given and the reactions involved.

### Step 1: Identify the Reaction of Metal with Oxygen
When a metal reacts with oxygen, it forms an oxide. The problem states that this oxide is a black solid.

**Hint:** Think about common metal oxides that are black in color.

### Step 2: Determine the Black Solid
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