Give reasons
A mixture of dilute NaOH and aluminium pieces is used to open drain.

Explanation

To understand why a mixture of dilute NaOH (sodium hydroxide) and aluminum pieces is used to open drains, we can break down the explanation into several steps:

### Step 1: Reaction Between Aluminum and Sodium Hydroxide
When aluminum (Al) reacts with dilute sodium hydroxide (NaOH), a chemical reaction occurs. The aluminum reacts with the hydroxide ions (OH⁻) present in the sodium hydroxide solution.

**Chemical Reaction:**
\[
2 \text{Al} + 2 \text{NaOH} + 6 \text{H}_2\text{O} \rightarrow 2 \text{Na[Al(OH)}_4] + 3 \text{H}_2
...