1. Radiation and Climate Incomplete Combustion 1

2. The products of hydrocarbon burning were shown as CO 2 and H 2 O when we did combustion reactions earlier this year. However, these are not the only possible products of combustion! When hydrocarbons undergo incomplete combustion, carbon monoxide (CO) and soot (C) also form. 2

3. Limiting Reactants Why might incomplete combustion occur? – One possible reason is that there is not enough oxygen gas available for complete combustion Not enough O atoms for every C to form CO 2 so CO forms instead – In such cases, oxygen would become the limiting reactant in the combustion process It limits the amount of hydrocarbon that can be completely burned. 3

4. Hot Dog Example Think about buying a package of hot dogs and a package of hot dog buns – Hot dogs are normally sold in packages of ten – Hot dog buns are normally sold in packages of eight Hot dog buns become the limiting reactant if you had just one package of each – They limit the number of hot dog sandwiches to eight sandwiches with two excess hot dogs. 4

5. HOMEWORK (Yup, that was really it) NOTE: Question 1 is review. Questions 2-4 focus on this PowerPoint and your previous knowledge of limiting reactants. 1) Many inexpensive sunglasses block visible light, but they do not block ultraviolet radiation. Explain the hazards of wearing such sunglasses at the beach or on a ski slope during a bright, sunny day. 5

6. HOMEWORK 2) If the air-fuel mixture is incorrect when using a Bunsen burner, the yellow flame will deposit black carbon on the bottom of a heating beaker of water. Explain why, in terms of limiting reactants. 6

7. HOMEWORK 3) Consider the following equation, which is part of a series of chemical changes used to recover sulfur from hydrogen sulfide (H 2 S) produced during crude-oil processing and natural-gas processing: 2 H 2 S + SO 2  3 S + 2 H 2 O + heat a.If 4.0 mol H 2 S and 3.0 mol SO 2 are the reactants, which is the limiting reactant? b.If 7.5 mol H 2 S and 2.8 mol SO 2 are the reactants, which is the limiting reactant? 7

8. HOMEWORK 4) Consider the equation shown in Question 3: a.What mass of H 2 S would be required to react completely with 205 g SO 2 ? b.If 45.4 kg SO 2 and 67.3 kg H 2 S were present in the reaction chamber, which would become the limiting reactant? 8