Heat of Combustion for C6H4O2: q (kJ/g) & q (kJ/mol)

[ahappel]

I am needing help on some homework questions:

A 2.200 g sample of quinone, C6H4O2, is burned in a bomb calorimeter whose total heat capacity is 7.854 kJ/ degrees C. The temperature of the calorimeter increases from 23.50 degrees C to 30.63 degrees C.

1. What is the HEAT OF COMBUSTION PER GRAM of quinone? (in kJ/g)

2. Per mole of quinone? (in kJ/mol)

 

[pikkie]

according to the rules in physics forum, we can't help those that didnt show their efforts. We are just guiding, not doing all the homework for you. you must at least show your way of calculations before we can help you.

 

[Blueshift5]

1. To calculate the heat of combustion per gram of quinone, we need to first calculate the heat released by the combustion of the 2.200 g sample of quinone. This can be done using the following formula:

q = m * C * ΔT

Where:
q = heat released (in kJ)
m = mass of quinone (in g)
C = heat capacity of the calorimeter (in kJ/ degrees C)
ΔT = change in temperature (in degrees C)

Substituting the given values, we get:

q = 2.200 g * 7.854 kJ/ degrees C * (30.63 degrees C - 23.50 degrees C)
q = 2.200 g * 7.854 kJ/ degrees C * 7.13 degrees C
q = 124.3 kJ

Now, to calculate the heat of combustion per gram of quinone, we need to divide this value by the mass of quinone used:

Heat of combustion per gram = 124.3 kJ / 2.200 g = 56.5 kJ/g

Therefore, the heat of combustion per gram of quinone is 56.5 kJ/g.

2. To calculate the heat of combustion per mole of quinone, we first need to calculate the number of moles of quinone used in the combustion:

Number of moles = mass / molar mass

Molar mass of quinone (C6H4O2) = 6*12.01 + 4*1.008 + 2*16.00 = 108.11 g/mol

Number of moles = 2.200 g / 108.11 g/mol = 0.0204 mol

Now, we can calculate the heat of combustion per mole of quinone by dividing the heat released by the number of moles:

Heat of combustion per mole = 124.3 kJ / 0.0204 mol = 6087 kJ/mol

Therefore, the heat of combustion per mole of quinone is 6087 kJ/mol.