Question

When 0.1523 g of liquid pentane (C5H12) combusts in a bomb calorimeter, the temperature rises from 23.7°C to 29.8°C. What is ΔUrxn for the reaction in kJ/mol pentane? The heat capacity of the entire bomb calorimeter is 5.23 kJ/°C.

Options:
a) -235.6
b) -189.2
c) 124.8
d) 301.4

Answer 1

To calculate the heat produced by the combustion of the benzene sample, use the equation ΔUrxn = -(qwater + qbomb). Calculate qwater using the equation qwater = (mwater × Cwater × ΔTwater), and qbomb using the equation qbomb = (Cbomb × ΔTbomb). Substitute the values into the equation for ΔUrxn and convert the result to kJ/mol pentane.

Step-by-step explanation:

To calculate the heat produced by the combustion of the benzene sample, we need to consider the heat absorbed by the bomb calorimeter and the water. The heat produced by the reaction can be calculated using the equation: ΔUrxn = -(qwater + qbomb). The heat absorbed by the water can be calculated using the equation: qwater = (mwater × Cwater × ΔTwater), where mwater is the mass of water, Cwater is the heat capacity of water, and ΔTwater is the change in temperature of the water.

The heat absorbed by the bomb calorimeter can be calculated using the equation: qbomb = (Cbomb × ΔTbomb), where Cbomb is the heat capacity of the calorimeter and ΔTbomb is the change in temperature of the calorimeter. After calculating qwater and qbomb, we can substitute the values into the equation for ΔUrxn and convert the result to kJ/mol pentane.

Using the given values of the mass of benzene (0.963 g), the change in temperature of the calorimeter (8.39 °C), and the heat capacity of the calorimeter (784 J/°C), we can calculate the heat produced by the combustion of the benzene sample.