Heats of Combustion

State the objective of experiment

This experiment’s goal is to determine the heat of combustion of naphthalene C₁₀H₈ as in the change in enthalpy from the combustion to determine exactly how much heat energy (in kJ) is released per mole (or gram) of naphthalene burned.

Outline the procedure

1. Compress 0.5 g of benzoic acid or naphthalene

2. Cut a 10 cm cotton thread and tie to the pellet tightly

3. Assemble the bomb, charge with oxygen, and load into bucket of calorimeter

4. Fill bucket with water with top exposed

5. Attach ignition leads and place lid

6. Stirrer should not make contact with the bucket or bomb, if grinding is heard, switch off stirrer, adjust calorimeter and try again.

7. Allow temperature readings to equibrate and record for one minute

8. once equibrated press ignition and record temp until stable about 10 mins

9. disasemble and vent and open bomb

10. repeat

List parts of the bomb calorimeter

Define heat capacity

The amount of heat energy required to raise the temperature of a specific object or substance by 1 degree Celsius

What is the difference between Cp and Cv?

specific heat capacity at a constant volumee

specific heat capacity at a constant pressure

Is combustion reaction exothermic or endothermic and why?

Exothermic b/c combustion releases thermal energy into its surroundings (Delta H < 0). This occurs because the total energy required to break the chemical bonds of the reactants ($\text{C}_{10}\text{H}_8$ and $\text{O}_2$) is less than the energy released

What is the purpose of the benzoic acid trials?

calibrate the bomb calorimeter. It allows you to experimentally determine the total heat capacity ($C_v$) of the calorimeter system (including the vessel, water, and thermometer), which is then used to calculate the unknown heat of combustion of naphthalene.