At constant volume, the heat of combustion of a particular compound is –3949.0 kJ/mol. When 1.331 g of this compound (molar mass = 141.44 g/mol) was burned in a bomb calorimeter, the temperature of the calorimeter (including its contents) rose by 3.837 °C. What is the heat capacity (calorimeter constant) of the calorimeter?
You change the sign of qcombustion rxn so that qcal = -qrxn.
qcal = Ccal x delta T
q = 3949*1.331/141.44 = ?
Then ? = Ccal*delta T. Solve for Ccal.
To calculate the heat capacity (calorimeter constant) of the calorimeter, we need to use the formula:
q = CΔT
where:
q is the heat absorbed or released by the calorimeter,
C is the heat capacity of the calorimeter, and
ΔT is the change in temperature of the calorimeter.
In this case, we know the heat released by the combustion of the compound (q) and the change in temperature (ΔT). We can use these values to calculate the heat capacity (C) of the calorimeter.
First, let's convert the mass of the compound burned to moles. We are given that the molar mass of the compound is 141.44 g/mol, and we have 1.331 g of the compound:
moles = mass / molar mass
= 1.331 g / 141.44 g/mol
≈ 0.0094 mol
Now, we can calculate the heat absorbed or released by the calorimeter (q) using the molar heat of combustion of the compound:
q = moles × molar heat of combustion
= 0.0094 mol × (-3949.0 kJ/mol)
≈ -37.06 kJ
Next, let's convert the change in temperature to degrees Kelvin (K), as temperature must be in Kelvin for calculations:
ΔT = 3.837 °C = 3.837 K
Now, we can rearrange the equation q = CΔT to solve for the heat capacity (C):
C = q / ΔT
= -37.06 kJ / 3.837 K
≈ -9.64 kJ/K
The heat capacity of the calorimeter (calorimeter constant) is approximately -9.64 kJ/K.