Nitromethane (CH3NO2) is a liquid fuel that is used in top fuel drag racing and model airplane engines. A 0.57g sample of nitromethane was placed in the constant volume (bomb) calorimeter. The temperature of the calorimeter rose from 23.25°C to 24.73°C. What is the enthalpy of combustion of nitromethane?
To calculate the enthalpy of combustion of nitromethane, we need to use the equation:
q = m × C × ΔT
where:
q = heat absorbed or released by the reaction
m = mass of the substance
C = specific heat capacity of the substance
ΔT = change in temperature
First, we need to find the heat absorbed or released by the reaction (q). In this case, since the calorimeter is constant volume (bomb calorimeter), the heat released by the combustion of nitromethane is equal to the heat absorbed by the calorimeter.
Next, we need to determine the specific heat capacity of the calorimeter (C). Generally, the specific heat capacity of a bomb calorimeter is provided in the problem. Let's assume it is given as 5.65 J/g°C.
Now, we can calculate the heat absorbed by the calorimeter using the mass (m) and the change in temperature (ΔT). Given that the mass of nitromethane is 0.57 g, and the change in temperature is 24.73°C - 23.25°C = 1.48°C:
q = 0.57 g × 5.65 J/g°C × 1.48°C
≈ 4.0046 J
The enthalpy change (ΔH) of the combustion reaction is equal to the heat absorbed or released by the reaction. Therefore, the enthalpy of combustion can be approximated to be 4.0046 J.