2.2016 gm of acetaldehyde produceed 13.95 Kcal of heat on combustion. The heat of combustion of `CH_(3)CHO` will be

Options

A. 279 kcal
B. 972 kcal
C. 27.9 kcal
D. 2.79 kcal

Answer

To find the heat of combustion of acetaldehyde (CH₃CHO), we can follow these steps:

### Step 1: Determine the molar mass of acetaldehyde (CH₃CHO)
The molar mass can be calculated as follows:
- Carbon (C): 12 g/mol (2 atoms)
- Hydrogen (H): 1 g/mol (4 atoms)
- Oxygen (O): 16 g/mol (1 atom)

Calculating the molar mass:
\[ \text{Molar mass of CH}_3\text{CHO} = (2 \times 12) + (4 \times 1) + (1 \times 16) = 24 + 4 + 16 = 44 \text{ g/mol} \]

### Step 2: Calculate the number of moles of acetaldehyde in 2.2016 g
Using the formula:
\[ \text{Number of moles} = \frac{\text{mass}}{\text{molar mass}} \]
Substituting the values:
\[ \text{Number of moles} = \frac{2.2016 \text{ g}}{44 \text{ g/mol}} \approx 0.05005 \text{ moles} \]

### Step 3: Calculate the heat released per mole of acetaldehyde
We know that 2.2016 g of acetaldehyde releases 13.95 kcal of heat. To find the heat released per mole:
\[ \text{Heat released per mole} = \frac{\text{Total heat released}}{\text{Number of moles}} \]
Substituting the values:
\[ \text{Heat released per mole} = \frac{13.95 \text{ kcal}}{0.05005 \text{ moles}} \approx 278.5 \text{ kcal/mol} \]

### Step 4: Round the result
We can round the result to a suitable number of significant figures:
\[ \text{Heat of combustion of CH}_3\text{CHO} \approx 279 \text{ kcal/mol} \]

### Final Answer
The heat of combustion of acetaldehyde (CH₃CHO) is approximately **279 kcal/mol**.

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