Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Name: ______________________________ Date: ______________ Honors Chemistry Period: _________ Hydrocarbons Activity Hydrocarbons are important fuels. They are often called “fossil fuels” because of their source. They react with oxygen to form carbon dioxide, water, and energy. 1. Write the general equation for a combustion reaction, assume “fossil fuel” is used: 2. The simplest hydrocarbons are the alkanes. Alkanes are called saturated hydrocarbons, because all the bonds between the atoms of alkanes are single covalent bonds. The formulas and names of the 5 smallest alkanes are given below. Use the model kits to build models of these molecules, and record the structures. a) methane, CH4 b) ethane, C2H6 c) propane, C3H8 d) butane, C4H10 e) pentane, C5H12 3. All of the alkanes have the general formula, CxH2x+2. a) Use this general formula to predict the formulas of some larger alkanes. Name Number of carbons Number of hydrogens Formula Hexane 6 Tridecane 13 ? 100 Octane b) Can you offer an explanation for the fact that there are 2x+2 hydrogens for every x carbons in an alkane? (Look at the structures for the pattern.) 1 Rev 09 Dec 2008 Name: ______________________________ Date: ______________ Honors Chemistry Period: _________ c) What is the hybridization for each of these molecules? 4. Notice the similarities in the names of the different alkanes. Describe how alkanes are named. In your description, make up a formula of an alkane not in this activity and give your alkane a name that fits the pattern. (See Chap 22) 5. Isomers are molecules with the same molecular formulas, but different structural formulas. The different arrangements of the atoms of isomers give the compounds slightly different properties. Alkanes can be straight chain or branched. Straight-chain means the carbons are all linked one after another. Branched refers to the branching of carbons off a longer chain. Branched alkanes are more valued in gasoline, and give gasoline a higher octane rating. Use the model kits to help you find the structure of the branched isomer of butane. a) Give its structural formula: b) Now use the model kits to find 2 branched isomers of pentane. Draw the structural formulas. 6. Alkenes are a type of unsaturated hydrocarbon, because they have less than the maximum number of hydrogen atoms. They are characterized by one carbon to carbon double bond. The general formula for an alkene is CxH2x. Use the model kits to determine the structure of the following alkenes and record the structural formulas. a) ethene, C2H4, b) propene, C3H6, 2 Rev 09 Dec 2008 Name: ______________________________ Date: ______________ Honors Chemistry Period: _________ c) butene, C4H8, d) draw another isomer of butene e) predict the name and formula of the alkene with 100 carbons f) What is the hybridization for each of these molecules? 3 Rev 09 Dec 2008 Name: ______________________________ Date: ______________ Honors Chemistry Period: _________ Bonus Challenge: Below is a table of the first 20 straight-chain alkanes and their properties. Complete the table, and then use it to answer the following questions: a) Which alkanes are gases at 25oC? b) Which alkanes are liquid at 25oC? c) Which alkanes are solid at 25oC? d) What is the relationship between the molar mass of alkanes and their melting and boiling points? (Write a complete sentence.) e) Explain the boiling point trend in terms of energy. Some Properties of the Alkanes Name Methane Ethane Propane n-Butane n-Pentane n-Hexane n-Heptane n-Octane n-Nonane n-Decane n-Undecane n-Dodecane n-Tridecane n-Tetradecane n-Pentadecane n-Hexadecane n-Heptadecane n-Octadecane n-Nonadecane n-Eicosane Formula CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22 M.P. (oC) Molar mass (g/mol) 16 30 44 58 72 86 100 114 128 142 -183 -172 -187 -138 -130 -95 -90.5 -57 -54 -30 -26 -10 -6 5.5 10 18 22 28 32 36 B.P. (oC) -162 -88.5 -42 0 36 69 98 126 151 174 196 216 235.4 253.7 270.63 287 301.8 316.1 329.7 343 Density @ 20oC (g/mL) 0.001432 0.0012291 0.0018024 0.0023758 0.626 0.659 0.684 0.703 0.718 0.730 0.740 0.749 0.7564 0.7628 0.769 0.773 0.7780 0.7768 0.7855 0.7886 For further study (extra credit), you may research other classes or types of hydrocarbons and report on their characteristics, such as identifying features, structural formulas, and naming. You might also include their industrial or biological importance. Other classes of hydrocarbons might include the alkynes, alcohols, carboxylic acids, etc. 4 Rev 09 Dec 2008