Chemical Reactions of the Alkanes

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AS - Level Chemistry (12 - Alkanes) Flashcards on Chemical Reactions of the Alkanes, created by Bee Brittain on 23/03/2016.
Bee Brittain
Flashcards by Bee Brittain, updated more than 1 year ago
Bee Brittain
Created by Bee Brittain over 8 years ago
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Question Answer
Draw the two types of bond in an alkane C-C and C-H bonds All sigma bonds
Why are Alkenes fairly unreactive? - They have strong C-C bonds and C-H bonds - C-C bonds are non-polar - The electronegativity of C and H is so similar the C-H bond can also be considered non-polar
Alkanes can take part in an exothermic reaction. What is the name of this reaction? Combustion
Name the products when an alkane is burned in a plentiful supply of oxygen - Carbon Dioxide - Water
Write out the word equation for the combustion of Ethane in a plentiful supply of Oxygen Ethane + Oxygen --> Carbon Dioxide + Water
Write out the symbol equation for when methane reacts with oxygen in a plentiful supply of oxygen. Include State Symbols. CH4 (g) + 2O2 (g) --> CO2 (g) + 2H2O (l)
Name the 3 products that can be produced when an alkane is burned in a limited supply of oxygen Water (H2O) Carbon Monoxide (CO) Carbon (C) (solid)
Why is carbon dioxide hard to detect and dangerous? It is hard to detect as it is colourless and odourless. It is dangerous because it is highly toxic.
Write out a symbol equation for the reaction between Heptane and oxygen in a limited supply of O2. (Include state symbols) C7H16 (g) + 7.5O2 (g) --> 7CO (g) + 8H2O (l)
When an alkane reacts with a halogen, what provides the initial energy to start the reaction? UV radiation
Reacting an alkane with a halogen is an example of what type of reaction? Substitution reaction
Draw out the symbol equation for when methane is reacted with bromine. (1 mark for correct equation) (1 mark for correct state symbols) CH4 (g) + Br2 (l) --> CH3Br (g) + HBr (g)
What is the name of the mechanism for the bromination of alkanes? Free Radical Substitution
What is the first step called in the mechanism for the bromination of alkanes? Initiation
The covalent bond in the bromine molecule is broken by what process? Where do the electrons go? Homolyctic Fission One electron from the (now broken) covalent bond goes to each Bromine atom
What is the end product of the initiation stage? two bromine radicals
Radicals don't have an electron pair, they just have one electron. What does this mean? They are extremely reactive and unstable
What is the second step in free radical substitution called? Propagation (there could be a couple of propagation steps)
Describe the first propagation step for the free radical substitution between bromine and methane Write a symbol equation for it Bromine radical reacts with a C-H bond in methane to form a methyl radical (CH3') and a molecule of hydrogen bromide CH4 + Br' --> CH3Br' + HBr
Describe the second propagation step for the free radical substitution between bromine and methane Write an equation for it Each methyl radical reacts with a molecule of Bromine to form bromomethane (CH3Br) and another *bromine radical (Br') *This new bromine radical means that the propagation steps can occur again and that is why it is a chain reaction CH3' + Br2 --> CH3Br + Br'
What is the third step of free radical substitution called? Termination
What happens in the final step of free radical substitution Two radicals react to form an element/compound with an electron pair
Give three examples of termination steps Br' + Br' --> Br2 CH3' + CH3' --> C2H6 CH3' + Br' --> CH3Br
Methane and Ethane have only one monosubstituted product. How many does monosubstituted isomers does pentane have? Three monosubstituted isomers. 1-bromopentane 2-bromopentane 3-bromopentane
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