🔍 Key Concepts

• complete vs. incomplete combustion of fuel oil • relationship between CO2, CO, and heat (energy) released • role of excess air and what a high CO2 reading in stack gas usually indicates

💭 Think About

• Compare the energy (heat) released when carbon burns fully to CO2 versus partially to CO. Which one gives more heat per unit of fuel? • Think about what a high CO2 reading in the stack tells you about how much of the carbon is being fully burned versus partially burned. • Which choice correctly links high CO2 with both combustion efficiency and the relative heat output compared to forming CO?

✅ Before You Answer

• Identify which reaction is more exothermic: C + O2 → CO2 or 2C + O2 → 2CO. • Make sure the option you pick connects high CO2 with efficient combustion, not just with air quantity alone. • Eliminate any choice that suggests CO formation gives equal or more heat than CO2 formation; verify which actually releases more heat.