Question

Consider the combustion of liquid c₅h₈ in oxygen gas to produce carbon dioxide gas and water vapor. In an experiment, 0.1063 g of c₅h₈ is combusted to produce enough heat to raise the temperature of 150.0 g of water by 7.638 °C. If -4794 J of heat was produced from the combustion of 0.001561 moles of c₅h₈, what is the enthalpy change (in kJ/mol) for the combustion of c₅h₈?

Answer 1

The enthalpy change for the combustion of C₅H₈ is -3070 kJ/mol, calculated using the heat produced from the experiment and the moles of C₅H₈ that combusted.

Step-by-step explanation:

To calculate the enthalpy change for the combustion of C₅H₈, the heat produced (-4794 J) and the amount of substance (0.001561 moles of C₅H₈) combusted in the reaction are used. The enthalpy change (ΔH) in kJ/mol for the reaction can be calculated with the formula ΔH = (q / n), where 'q' is the heat exchanged during the reaction and 'n' is the number of moles. Thus the calculation is ΔH = (-4794 J) / (0.001561 moles) which then must be converted from J to kJ by dividing by 1000, giving ΔH = -3070 kJ/mol. This represents the enthalpy of combustion of C₅H₈ per mole.