Chemistry Practice Problems Enthalpy of Formation Practice Problems Solution: A city of 100,000 people uses approximately 1.0 x ...

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Solution: A city of 100,000 people uses approximately 1.0 x 1011 kJ of energy per day (an exothermic process). Suppose all of that energy comes from the combustion of liquid octane (C8H18). Use the given standard enthalpies of formation to find the ∆H for the combustion of octane and then determine how many kg of octane would be necessary to provide that amount of energy.                   C8H18   +   25/2 O2   →   8 CO2   +   9 H2O∆H for octane = -250.1 kJ/mol∆H for carbon dioxide = -393.5 kJ/mol∆H for water = -241.8 kJ/mol

Problem

A city of 100,000 people uses approximately 1.0 x 1011 kJ of energy per day (an exothermic process). Suppose all of that energy comes from the combustion of liquid octane (C8H18). Use the given standard enthalpies of formation to find the ∆H for the combustion of octane and then determine how many kg of octane would be necessary to provide that amount of energy.

                   C8H18   +   25/2 O2   →   8 CO2   +   9 H2O

∆H for octane = -250.1 kJ/mol

∆H for carbon dioxide = -393.5 kJ/mol

∆H for water = -241.8 kJ/mol