Final answer:
The change in enthalpy (ΔH) for the combustion of benzoic acid in the bomb calorimeter is calculated to be -3227.86 kJ/mol. This was determined by measuring the heat absorbed by the calorimeter and dividing by the moles of benzoic acid combusted.
Step-by-step explanation:
To calculate the change in enthalpy (ΔH) for the combustion reaction of benzoic acid (C6H5COOH) in kJ/mol, we can use the provided heat capacity of the calorimeter and the temperature change observed during the reaction. First, we need to find the total amount of heat (q) absorbed by the calorimeter, which can be calculated using the formula q = calorimeter heat capacity (∘ΔT), where ΔT is the temperature change.
The total heat absorbed by the calorimeter is:
q = 5.020 kJ/°C × (31.67°C - 25.24°C) = 5.020 kJ/°C × 6.43°C = 32.2786 kJ
Next, we calculate the enthalpy change per mole of benzoic acid. We know the mass of benzoic acid combusted is 1.221 g. The molar mass of benzoic acid is 122.12 g/mol, thus:
Moles of benzoic acid = 1.221 g / 122.12 g/mol = 0.01 mol
Now, to find ΔH in kJ/mol, we divide the total heat released by the moles of benzoic acid:
ΔH = 32.2786 kJ / 0.01 mol = 3227.86 kJ/mol
Since combustion is an exothermic reaction, ΔH is negative, so the final ΔH for the reaction is -3227.86 kJ/mol.