Dihydrogen can be prepared by heating Al with water.

Answer

To prepare dihydrogen (H2) by heating aluminum (Al) with water (H2O), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this reaction are aluminum metal (Al) and water (H2O).

2. **Write the Reaction**: The basic reaction can be written as:
\[ \text{Al} + \text{H}_2\text{O} \rightarrow \text{H}_2 + \text{Al}_2\text{O}_3 \]
Here, aluminum reacts with water to produce dihydrogen and aluminum oxide.

3. **Heat the Mixture**: When aluminum is heated in the presence of water, it reacts to produce dihydrogen gas (H2) and aluminum oxide (Al2O3).

4. **Balance the Reaction**: To ensure the law of conservation of mass is followed, we need to balance the chemical equation. The unbalanced equation is:
\[ \text{Al} + \text{H}_2\text{O} \rightarrow \text{H}_2 + \text{Al}_2\text{O}_3 \]
- Count the number of atoms for each element on both sides.
- There are 2 aluminum atoms in Al2O3, so we need 2 Al on the reactant side.
- There are 3 oxygen atoms in Al2O3, so we need 3 H2O on the reactant side to provide enough oxygen.
- This gives us 6 hydrogen atoms from 3 H2O, so we need 3 H2 on the product side.

The balanced equation will be:
\[ 2\text{Al} + 6\text{H}_2\text{O} \rightarrow 3\text{H}_2 + 2\text{Al}_2\text{O}_3 \]

5. **Conclusion**: The balanced reaction shows that 2 moles of aluminum react with 6 moles of water to produce 3 moles of dihydrogen and 2 moles of aluminum oxide.