Enthalpy of Combustion Cycles - Thermodynamics Pt B (3.2)

Question 1

What is the enthalpy of combustion?

Answer 1

• when 1 mole of a substance = burnt in excess oxygen under standard conditions

Question 2

In an enthalpy cycle for combustion, what happens?

Answer 2

• both arrows go down as conbustion always destroys things

Question 3

What are the steps for drawing combustion cycles?

Answer 3

• write balanced reaction equations at the top with state symbols
• write comcustion products in their standard states in a box at the bottom (balnce carbon & hydrogen)
• add oxygen to the reactants & products so that everything balnces
• draw arrows from each product/reactant to the combustion product (not O2)
• label each arrow with enthalpy of combustion data (GIQ)
• Multiply by the number of moles as enthalpy changes = per mole