Malonic acid
`overset(P_(2)O_(5))underset(150^(@)C)rarr" Foul smell"(A)overset(200^(@)C)rarr(B)+"Carbon"`
The total number of `sigma` and `Pi` bonds present in compound A are :

Answer

To solve the problem, we need to analyze the reaction of malonic acid with phosphorus pentoxide (P2O5) and determine the structure of compound A formed in the process. Then, we will count the total number of sigma (σ) and pi (π) bonds in that compound.

### Step-by-Step Solution:

1. **Identify the Structure of Malonic Acid**:
Malonic acid has the formula C3H4O4 and its structure can be represented as:
\[ \text{HOOC-CH2-COOH} \]
This structure consists of two carboxylic acid groups (-COOH) and a methylene group (-CH2-).

2. **Reaction with P2O5**:
When malonic acid is heated with P2O5 at 150°C, it undergoes dehydration to form carbon suboxide (C3O2) and phosphoric acid (H3PO4). The reaction can be summarized as:
\[ \text{C3H4O4} \xrightarrow{P2O5, 150°C} \text{C3O2} + \text{H3PO4} \]

3. **Determine the Structure of Carbon Suboxide (C3O2)**:
The structure of carbon suboxide can be represented as:
\[ O=C=C=C=O \]
This compound has alternating double bonds between carbon atoms and oxygen.

4. **Count Sigma (σ) and Pi (π) Bonds in C3O2**:
- **Sigma Bonds (σ)**:
- Each double bond consists of one sigma bond.
- There are 3 carbon-carbon double bonds and 2 carbon-oxygen double bonds.
- Total sigma bonds = 3 (C=C) + 2 (C=O) = 5 σ bonds.
- **Pi Bonds (π)**:
- Each double bond consists of one pi bond.
- Total pi bonds = 3 (C=C) + 2 (C=O) = 5 π bonds.

5. **Final Count of Bonds**:
- Total number of sigma bonds = 5
- Total number of pi bonds = 5

Thus, the total number of sigma and pi bonds present in compound A (C3O2) is:
\[ \text{Total Bonds} = 5 \sigma + 5 \pi \]

### Final Answer:
The total number of sigma and pi bonds present in compound A is **5 σ + 5 π**.