Question

1.

A bomb calorimeter, or a constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods.

In an experiment, a 0.4137 g sample of bianthracene (C₂₈H₁₈) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.361×10³ g of water. During the combustion the temperature increases from 24.82 to 27.25 °C. The heat capacity of water is 4.184 J g^-1°C^-1.

The heat capacity of the calorimeter was determined in a previous experiment to be 760.2 J/°C.

Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of bianthracene based on these data.

C₂₈H₁₈(s) + (65/2) O₂(g) > 9 H₂O(l) + 28 CO₂(g) + Energy

Molar Heat of Combustion =    kJ/mol

2.

A bomb calorimeter, or constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods.

Since the "bomb" itself can absorb energy, a separate experiment is needed to determine the heat capacity of the calorimeter. This is known as calibrating the calorimeter.

In the laboratory a student burns a 0.831-g sample of glutaric acid (C₅H₈O₄) in a bomb calorimeter containing 1110. g of water. The temperature increases from 25.40 °C to 27.90 °C. The heat capacity of water is 4.184 J g^-1°C^-1.

The molar heat of combustion is −2151 kJ per mole of glutaric acid.

C₅H₈O₄(s) + 5 O₂(g) >5 CO₂(g) + 4 H₂O(l) + Energy

Calculate the heat capacity of the calorimeter.

heat capacity of calorimeter =  J/°C

3.

A bomb calorimeter, or a constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods.

In an experiment, a 0.7263 g sample of para-benzoquinone (C₆H₄O₂) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.225×10³ g of water. During the combustion the temperature increases from 28.02 to 30.95 °C. The heat capacity of water is 4.184 J g^-1°C^-1.

The heat capacity of the calorimeter was determined in a previous experiment to be 884.1 J/°C.

Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of para-benzoquinone based on these data.

C₆H₄O₂(s) + 6O₂(g) > 2 H₂O(l) + 6 CO₂(g) + Energy

Molar Heat of Combustion =    kJ/mol

Answer 1

mass of water = 1.361×10³ g

dT = T2 -T1 = 27.25 - 24.82 = 2.43

dT = 17.9 oC

Q = ( m Cp dT ) _solution + ( Cp dT ) _calorimeter

Q = 1.361 x 10^3 x 4.184 x 2.43 + 760.2 x 2.43

Q = 15684.7 J

Q = 15.685 kJ

moles of bianthracene = 0.4137 / 354 = 1.168 x 10^-3

deltaHrxn = - Q / n

             = - 15.685 / 1.168 x 10^-3

             = -13421.5 kJ / mol

Molar Heat of Combustion = -13421.5 kJ / mol