Question

When 1.01 g of octane, C₈H₁₈​, is burned in a constant-volume bomb calorimeter, the temperature increases by 5.0°C. The heat capacity of the bomb calorimeter is 9.69 kJ/°C. Calculate the molar heat of combustion of octane in kJ/mol. (molar mass of C₈H₁₈​=114 g/mol )

A. −5.47×10³ kJ/mol
B. −4.21×10² kJ/mol
C. −8.32×10³ kJ/mol
D. −4.85×10⁴ kJ/mol
E. −3.23×10⁵ kJ/mol

Answer 1

To calculate the molar heat of combustion of octane, you can use the formula Q = mcΔT, where Q is the heat released, m is the mass of octane, c is the heat capacity of the bomb calorimeter, and ΔT is the change in temperature. Using this formula, the molar heat of combustion of octane is approximately -5.50 × 10³ kJ/mol.

Step-by-step explanation:

To calculate the molar heat of combustion of octane, we need to use the given information and perform some calculations. First, we can calculate the amount of heat released by the combustion of 1.01 g of octane using the formula:

Q = mcΔT

Where,
Q = heat released by the combustion
m = mass of octane
c = heat capacity of the bomb calorimeter
ΔT = change in temperature

Plugging in the values, we get:

Q = (1.01 g)(9.69 kJ/°C)(5.0°C) = 48.55 kJ

Next, we can calculate the molar heat of combustion by dividing the heat released by the number of moles:

Molar heat of combustion = (48.55 kJ) / (1.01 g / 114 g/mol) = -549.95 kJ/mol

Therefore, the molar heat of combustion of octane is approximately -549.95 kJ/mol, which can be rounded to -5.50 × 10³ kJ/mol.