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Chapter 11 Introduction to Organic Chemistry: Alkanes

Chapter 11 Introduction to Organic Chemistry: Alkanes. 11.4 Properties of Alkanes. Some Properties of Alkanes. The properties of alkanes include being nonpolar insoluble in water less dense than water flammable in air. Alkanes with 1 – 4 Carbon Atoms.

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Chapter 11 Introduction to Organic Chemistry: Alkanes

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  1. Chapter 11 Introduction to Organic Chemistry: Alkanes 11.4Properties of Alkanes

  2. Some Properties of Alkanes The properties of alkanes include being • nonpolar • insoluble in water • less dense than water • flammable in air

  3. Alkanes with 1–4 Carbon Atoms Alkanes with 1–4 carbon atoms are • methane, ethane, propane, and butane • gases at room temperature • used as heating fuels

  4. Alkanes with 5–17 Carbon Atoms Alkanes with 5–8 carbon atoms are • liquids at room temperature • pentane, hexane, heptane, and octane • very volatile • used to make gasoline Alkanes with 9–17 carbon atoms • are liquids at room temperature • have higher boiling points • are found in kerosene, diesel, and jet fuels

  5. Alkanes with 18 or More Carbon Atoms Alkanes with 18 or more carbon atoms • have high molar masses • are waxy solids at room temperature • are used in waxy coatings of fruits and vegetables

  6. Boiling Points of Alkanes Boiling points of alkanes • are lowest of the organic compounds • increase with larger molecules due to increased dispersion forces • decrease for branched alkanes • increase for cycloalkanes

  7. Boiling Points of Alkanes with 5 Carbons

  8. Learning Check For the following pairs of hydrocarbon, which one has the higher boiling point? Why? A. Butane or octane B. Hexane or 2,3-dimethylbutane

  9. Solution For the following pairs of hydrocarbon, which one has the higher boiling point? Why? A. Butane or octane octane (has more carbon atoms) B. Hexane or 2,3-dimethylbutane hexane (both have 6 carbons, but hexane is not branched)

  10. Crude Oil The hydrocarbons in crude oil are • separated by their different boiling points • heated to higher temperatures to produce gases that can be cooled and removed

  11. Crude Oil (continued)

  12. Combustion of Alkanes Alkanes • undergo combustion by reacting with oxygen to produce carbon dioxide, water, and energy • are typically not very reactive due to strong C—C single bonds Alkane + O2(g) CO2(g) + H2O(g) + energy

  13. Balancing A Combustion Equation Write the equation: C5H12(l) + O2(g) CO2(g) + H2O(g) Balance C: C5H12(l) + O2(g) 5CO2(g) + H2O(g) Balance H: C5H12(l) + O2(g) 5CO2(g) +6H2O(g) Balance O with O2: C5H12(l) + 8O2(g) 5CO2(g) + 6H2O(g)

  14. Learning Check Propane is used to provide heat for cooking or warminga room. Write a balanced equation for the complete combustion of propane.

  15. Solution Unbalanced equation: C3H8(g) + O2(g) CO2(g) + H2O(g) Balance C: C3H8(g) + O2(g) 3CO2(g) + H2O(g) Balance H: C3H8(g) + O2(g) 3CO2(g) + 4H2O(g) Balance O: C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)

  16. Learning Check Write a balanced equation for the reaction for the complete combustion of heptane, C7H16.

  17. Solution Write a balanced equation for the reaction for thecomplete combustion of heptane, C7H16. C7H16(l) + O2(g) CO2(g) + H2O(g) C7H16(l) + O2(g) 7CO2(g) + 8H2O(g) C7H16(l) + O2(g) 7CO2(g) + 8H2O(g) C7H16(l) + 11O2(g) 7CO2(g) + 8H2O(g) Balanced equation: C7H16(l) + 11O2(g) 7CO2(g) + 8H2O(g)

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