Thermodynamic Problem Kill me! plz help?

Question

Toluene, C7H8, is used in the manufacture of explosives such as TNT (trinitrotoluene). A 1.500 g sample of liquid toluene was placed in a bomb calorimeter along with excess oxygen. When the combustion of the toluene was initiated, the temperature of the calorimeter rose from 25.000°C to 26.413°C. The products of the combustion are CO2(g) and H2O(l), and the heat capacity of the calorimeter was 45.06 kJ°C-1. The reaction was
C7H8(l) + 9O2(g) 7CO2(g) + 4H2O(l).

1) The number of joules liberated by reaction of the 1.500 g of toluene is __?___.

2) The number of joules that would be liberated under similar conditions if 1.000 mol of toluene were burned is __?___.

If you could explain or show work, greatly appreciated. Thank you!

Answer 1

From the heat capacity of the calorimeter and the delta T of the combustion, you can calculate the energy released by the reaction.

Since the calorimeter temperature went up by 1.413°C, and each 1°C requires 45.06 kJ of heat, then the product of those is the amount of heat released by the reaction.

1.413 °C X 45.06 kJ/°C = 63.67 kJ = 63670 J released.

2) Since the molar mass of toluene is 92.15 g/mol, and since you combused 1.500 grams, you can get to the J/mol by:

(63670 J/1.500 g) X 92.15 g/mol = 3.911 X 10^6 J liberated/mol of toluene


Hope this helps....