`1 g` of an alloy of `Al` and `Mg` reacts with excess `HCl` to form `AlCl_(3)`, `MgCl_(2)`, and `H_(2)`. The evolved `H_(2)` collected over mercury at `0^(@)C` occupied `1200 mL` at `699 mm Hg`. What is the composition of alloy?

Explanation

To determine the composition of the alloy of Aluminum (Al) and Magnesium (Mg) that reacts with excess hydrochloric acid (HCl) to produce Aluminum chloride (AlCl3), Magnesium chloride (MgCl2), and Hydrogen gas (H2), we can follow these steps:

### Step 1: Write the Balanced Chemical Reactions
The reactions for Aluminum and Magnesium with HCl can be represented as follows:

1. For Aluminum:
\[
2 \text{Al} + 6 \text{HCl} \rightarrow 2 \text{AlCl}_3 + 3 \text{H}_2
...