The heat evolved in the combustion of benzene is given by the equation:
`C_(6)H_(6)(g) + (15)/(2) O_(2)(g) to 6CO_(2)(g) + 3H_(2)O(l), DeltaH = - 3264.6 kJ "mol"^(-1)`
The heat energy changes when 39 g of `C_(6)H_(6)` are burnt im an open ontainer will be:

Options

A. `+ 816.15 kJ "mol"^(-1)`
B. `+ 1632.3 kJ "mol"^(-1)`
C. `-1632.3 kJ "mol"^(-1)`
D. `-2448.45 kJ "mol"^(-1)`

Explanation

To determine the heat energy change when 39 g of benzene (C₆H₆) is burnt, we can follow these steps:

### Step 1: Calculate the molar mass of benzene (C₆H₆)
The molecular formula of benzene is C₆H₆. To find its molar mass:
- Carbon (C) has an atomic mass of approximately 12 g/mol. There are 6 carbon atoms in benzene.
- Hydrogen (H) has an atomic mass of approximately 1 g/mol. There are 6 hydrogen atoms in benzene.

Calculating the molar mass:
\[ \text{Molar mass of C₆H₆} = (6 \times 12) + (6 \times 1) = 72 + 6 = 78 \text{ g/mol} \]

### Step 2: Determine the heat evolved per gram of benzene
The heat evolved during the combustion of 1 mole of benzene is given as ΔH = -3264.6 kJ/mol. Since 1 mole of benzene weighs 78 g, we can find the heat evolved per gram:
\[ \text{Heat evolved per gram} = \frac{-3264.6 \text{ kJ}}{78 \text{ g}} \approx -41.8 \text{ kJ/g} \]

### Step 3: Calculate the heat evolved for 39 g of benzene
Now, we can calculate the heat evolved when 39 g of benzene is burnt:
\[ \text{Heat evolved for 39 g} = 39 \text{ g} \times -41.8 \text{ kJ/g} \approx -1630.2 \text{ kJ} \]

### Final Answer
The heat energy change when 39 g of benzene is burnt in an open container is approximately **-1630.2 kJ**.

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