`HCHO` and `HCOOH` are detected by

Options

A. `NaHCO_(3)`
B. `CuSO_(4)//NaOH`
C. `AgNO_(3)//NH_(4)OH`
D. All of these

Answer

To detect formaldehyde (HCHO) and formic acid (HCOOH), we can use specific reagents that will react differently with these compounds. Here's a step-by-step solution:

### Step 1: Understanding the Compounds
- **Formaldehyde (HCHO)**: It is an aldehyde and can be oxidized.
- **Formic Acid (HCOOH)**: It is a carboxylic acid and can release carbon dioxide when reacted with a bicarbonate.

### Step 2: Detecting Formic Acid
- **Using Sodium Bicarbonate (NaHCO3)**: When formic acid reacts with sodium bicarbonate, it produces carbon dioxide (CO2) gas. This reaction can be represented as:
\[ \text{HCOOH} + \text{NaHCO}_3 \rightarrow \text{NaCOO}^- + \text{H}_2\text{O} + \text{CO}_2 \uparrow \]
- **Observation**: The evolution of CO2 gas indicates the presence of formic acid.

### Step 3: Detecting Formaldehyde
- **Using Tollens' Reagent**: Tollens' reagent (Ag(NH3)2^+) is used to detect aldehydes. When formaldehyde is treated with Tollens' reagent, it gets oxidized to formic acid, and silver ions are reduced to metallic silver, which deposits as a silver mirror.
- **Reaction**:
\[ \text{HCHO} + 2 \text{Ag(NH}_3)_2^+ + 2 \text{OH}^- \rightarrow \text{HCOO}^- + 2 \text{Ag} + 2 \text{NH}_3 + 2 \text{H}_2\text{O} \]
- **Observation**: The formation of a silver mirror indicates the presence of formaldehyde.

### Step 4: Summary of Detection Methods
- **Formic Acid**: Detected by the evolution of CO2 when reacted with sodium bicarbonate.
- **Formaldehyde**: Detected by the formation of a silver mirror when reacted with Tollens' reagent.

### Final Answer
- **Formic Acid (HCOOH)** is detected using **sodium bicarbonate**.
- **Formaldehyde (HCHO)** is detected using **Tollens' reagent**.

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