The complete combustion of 1.283g of cinnamaldeyde (C9H8O, one of the compounds in cinnamon) in a bomb calorimeter (Ccalorimeter=3.841 kJ/C) produced an increase in temperature of 130.32 C. Calculate the molar enthalpy of combustion of cinnamaldehydy (delta H comb) (in kilojoules per mole on cinnamaldehyde)
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To calculate the molar enthalpy of combustion (ΔHcomb) of cinnamaldehyde, we need to use the following equation:
ΔHcomb = Qcomb / n
Where:
ΔHcomb is the molar enthalpy of combustion (in kJ/mol)
Qcomb is the heat released in the combustion process (in kJ)
n is the number of moles of cinnamaldehyde burned
First, we need to find the heat released in the combustion process, which can be calculated using the specific heat capacity of the bomb calorimeter (Ccalorimeter) and the temperature change (ΔT):
Qcomb = Ccalorimeter * ΔT
Let's plug in the values given in the question:
Ccalorimeter = 3.841 kJ/°C (convert to kJ/K by dividing by 1, as °C and K have the same unit)
ΔT = 130.32 °C
Ccalorimeter = 3.841 kJ/K
ΔT = 130.32 °C
Now, we need to convert the mass of cinnamaldehyde (1.283g) to moles (n) using the molar mass of cinnamaldehyde (C9H8O):
Molar mass of C9H8O = (9 * atomic mass of C) + (8 * atomic mass of H) + (1 * atomic mass of O)
Atomic mass of C = 12.01 g/mol
Atomic mass of H = 1.008 g/mol
Atomic mass of O = 16.00 g/mol
Molar mass of C9H8O = (9 * 12.01) + (8 * 1.008) + (1 * 16.00)
Now that we have the molar mass of cinnamaldehyde, we can calculate the number of moles:
n = mass / molar mass
n = 1.283g / molar mass of C9H8O
Finally, we can substitute the values into the equation for ΔHcomb:
ΔHcomb = Qcomb / n