A constant pressure calorimeter having a heat capacity of 60.8 kJ/K is used to measure the energy released from burning a compound in excess oxygen to form CO2(g) and H2O(l). If the enthalpy of combustion of the compound is -2914.0 kJ/mol and the temperature of the calorimeter rises from 25.14 C to 26.79 C, how many moles of the compound were oxidized?
heat in combustion as measured by the calorimeter = 60.8 kJ/K x (delta T) = ? kJ released.
?kJ released/deltaH in kJ/mol = #moles.
To answer this question, we need to apply the principle of heat transfer in a calorimeter.
The heat released during the combustion reaction is transferred to the calorimeter, which causes a change in its temperature. The heat capacity of the calorimeter (C) is the amount of energy required to raise its temperature by 1 Kelvin or 1 degree Celsius.
The formula to calculate the heat transfer is:
q = C * ΔT
where q is the heat transfer, C is the heat capacity, and ΔT is the change in temperature.
In this case, we have the heat capacity of the calorimeter (C = 60.8 kJ/K), and the change in temperature (ΔT = 26.79 °C - 25.14 °C = 1.65 °C).
Now, we need to calculate the heat transfer (q) using the formula mentioned above:
q = 60.8 kJ/K * 1.65 °C = 100.32 kJ
The enthalpy of combustion of the compound is given as -2914.0 kJ/mol. This value represents the heat released per mole of the compound. Therefore, we can calculate the number of moles (n) of the compound using the following formula:
q = ΔH * n
where ΔH is the enthalpy change per mole and n is the number of moles.
Now, let's rearrange the equation to solve for n:
n = q / ΔH
n = 100.32 kJ / -2914.0 kJ/mol ≈ -0.0345 mol
Since the number of moles cannot be negative, we take the absolute value:
n ≈ 0.0345 mol
Therefore, approximately 0.0345 moles of the compound were oxidized.