Write the structures of the main products when `CH_(3)CH_(2)CHO` reacts with the following reagents :
(i) `Zn-Hg//"Conc".HCl` , (ii) `H_(2)N-OH//H^(+)` , (iii)`HCN`

Explanation

To solve the problem, we will analyze the reaction of the compound `CH3CH2CHO` (which is propanal) with three different reagents.

### Step 1: Reaction with `Zn-Hg//"Conc".HCl`
1. **Identify the reaction type**: The reaction of an aldehyde with zinc amalgam in the presence of concentrated hydrochloric acid is known as Clemmensen reduction. This reaction reduces the carbonyl group (C=O) to a methylene group (–CH2–).
2. **Write the structure of the reactant**: The reactant is propanal, which can be represented as:
\[ \text{CH}_3\text{CH}_2\text{CHO} \]
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