Which of the following statements is/are correct about formic acid?

Options

A. a.It reduces Tollens reagent.
B. b.It gives `CO` and `H_(2)O` on heating with conc. `H_(2)SO_(4)`.
C. c.It is a stronger acid than benzoic acid
D. d.It forms formyl chloride with `PCl_(5)`.

Explanation

### Step-by-Step Solution

To determine which statements about formic acid are correct, we will analyze each statement one by one.

1. **Statement A: Formic acid reduces Tollens' reagent.**
- Formic acid (HCOOH) contains the aldehyde functional group (C=O with an -OH group), which is characteristic of aldehydes.
- Aldehydes are known to reduce Tollens' reagent (Ag(NH3)2OH), resulting in the formation of a silver mirror or precipitate of silver metal.
- Therefore, this statement is **correct**.

2. **Statement B: Formic acid gives CO and H2O on heating with concentrated H2SO4.**
- When formic acid is heated with concentrated sulfuric acid (H2SO4), it undergoes dehydration.
- The concentrated H2SO4 acts as a dehydrating agent, removing water (H2O) from formic acid, leading to the formation of carbon monoxide (CO) and water.
- Thus, this statement is also **correct**.

3. **Statement C: Formic acid is a stronger acid than benzoic acid.**
- Formic acid (HCOOH) is indeed a stronger acid than benzoic acid (C6H5COOH).
- This is due to the resonance stabilization of the carboxylate ion formed after deprotonation. In benzoic acid, the resonance involves the aromatic ring, which stabilizes the benzoate ion less effectively than the resonance in formic acid.
- Therefore, this statement is **correct**.

4. **Statement D: Formic acid forms formaldehyde chloride with PCl5.**
- When formic acid reacts with phosphorus pentachloride (PCl5), it does not form formaldehyde chloride (HCOCl) because this compound is unstable and does not exist.
- Instead, the reaction typically leads to the formation of acid chlorides, but in this case, the specific product does not form.
- Thus, this statement is **incorrect**.

### Conclusion
The correct statements about formic acid are A, B, and C. Statement D is incorrect.