The enthalpy of combustion of benzoic acid (C6H5CO2H) is –3228 kJ/mol. The burning of 1.698 g of benzoic acid in a calorimeter causes the temperature to increase by 2.865 ºC. What is the heat capacity (in kJ/ºC) of the calorimeter?
mols benzoic acid = grams/molar mass = ?
Then q = mols benz acid x Ccal(delta T)
q is +3238 kJ. Substitute and solve for Ccal.
To find the heat capacity of the calorimeter, we need to use the equation:
q = m × C × ΔT,
where q is the heat absorbed or released by the system (calorimeter), m is the mass of the substance being burned (benzoic acid), C is the heat capacity of the calorimeter, and ΔT is the change in temperature.
First, we need to convert the mass of benzoic acid to moles. The molar mass of benzoic acid (C6H5CO2H) is 122.12 g/mol.
1.698 g × (1 mol / 122.12 g) = 0.0139 mol
Next, we need to calculate the heat absorbed or released by the system (q). We can use the enthalpy of combustion of benzoic acid to do this. The given enthalpy of combustion is –3228 kJ/mol.
q = ΔH × n,
where ΔH is the enthalpy of combustion and n is the number of moles of benzoic acid.
q = –3228 kJ/mol × 0.0139 mol = –44.85 kJ
Now, we can substitute the values into the equation to solve for the heat capacity (C).
–44.85 kJ = (C) × 2.865 ºC
C = –44.85 kJ / 2.865 ºC = –15.66 kJ/ºC
Therefore, the heat capacity of the calorimeter is –15.66 kJ/ºC.