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level: Level 1 of Alkanes

Questions and Answers List

level questions: Level 1 of Alkanes

QuestionAnswer
Shapes of alkanesevery single carbon has 4 bonds so tetrahedral 109.5 degrees
General formula of alkanesCn H2n+2
Bonding in Alkanes-single covalent -overlapping orbitals so sigma bonds
Effect of chain length and branching- CHAIN LENGH INCREASES = MORE LONDON FORCES = SO MORE ENERGY REQUIRED = HIGHER BOLING POINT -BRANCHES = MORE SURFACE CONTACT POINTS= LESS ENERGY REQUIRED TO OVERCOME THE INTERMOLECULAR FORCES= LOWER BOILING POINT
The combustion of alkanesThe moles of CO2 tell you the number of carbon atoms in the alkane The moles of water tell you half the amount their is of Hydrogen in the alkane
Incomplete combustion exampleC6H14 + 7/202 ---> 6CO + 7H20
Complete combustion exampleCH4 + 202 ----> C02 + 2H20
Heterolytic fissionbond breaks unevenly CL - Cl = CL+ AND CL- as one gains and both electrons
Homolytic fissionBonds break evenly CL-CL = CL- AND CL- each takes one electron so it is unpaired leaving a very reactive RADICAL
Halogenation of alkanesAlkanes react with halogens under UV light -radical substitution
Chlorination stepsInitiation: The halogen (cl-cl) bond is broken by homolytic fission forming two radicals CL* + CL* Propagation: 1. CH4 + Cl* ---> CH3 * + HCL 2.CH3* + CL2 ----> CH3Cl + CL* Termination: The cancellations of radicals for the initiation eq 1. CL* + CL* = CL2 2.CH3* + CH3*= C2H6 3.CH3* + CL* =CH3CL