4.1.2 - Alkanes Flashcards
What is the general formula for alkanes?
The general formula for alkanes is CₙH₂ₙ₊₂.
What type of bond do alkanes have between carbon atoms?
Alkanes have single covalent bonds, known as sigma bonds (σ-bonds), between carbon atoms.
What is meant by the term “saturated hydrocarbon”?
A saturated hydrocarbon is a compound made up of only carbon and hydrogen atoms, with single bonds between the carbon atoms (as in alkanes).
Why are alkanes relatively unreactive?
Alkanes are relatively unreactive due to the strong C–C and C–H bonds and the lack of a polar functional group.
What is the process called when alkanes react with oxygen?
The process is called combustion.
What are the products of the complete combustion of alkanes?
The products of the complete combustion of alkanes are carbon dioxide (CO₂) and water (H₂O).
What is the combustion of alkanes in limited oxygen?
In limited oxygen, the combustion of alkanes produces carbon monoxide (CO) and water (H₂O).
What is cracking in relation to alkanes?
Cracking is the process of breaking down large alkane molecules into smaller molecules, including alkenes and shorter-chain alkanes.
What are the main uses of alkanes?
Alkanes are mainly used as fuels (e.g., methane, propane, and butane) and as starting materials for other chemicals.
What is the boiling point trend in alkanes?
The boiling point of alkanes increases as the number of carbon atoms increases, due to stronger van der Waals forces.
What is the structure of methane (CH₄)?
Methane (CH₄) has a tetrahedral structure, with carbon in the center and four hydrogen atoms bonded to it.
How does branching affect the boiling point of alkanes?
More branching in alkanes lowers the boiling point because the molecules have fewer points of contact, leading to weaker van der Waals forces.
What is the main method of producing alkanes?
Alkanes are mainly produced through the fractional distillation of crude oil.
What are isomers in alkanes?
Isomers are compounds that have the same molecular formula but different structural arrangements of atoms.
What is the combustion reaction for propane (C₃H₈)?
The complete combustion of propane is:
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.
What is the general reaction for the halogenation of alkanes?
The general reaction for halogenation is:
Alkane + Halogen → Haloalkane + Hydrogen halide.
What conditions are required for the halogenation of alkanes?
The halogenation of alkanes requires ultraviolet (UV) light or heat to initiate the reaction.
What is a free radical in the context of alkane reactions?
A free radical is a highly reactive species with an unpaired electron, often involved in chain reactions like halogenation.
What is the mechanism of halogenation of alkanes?
The mechanism of halogenation is a free radical substitution mechanism involving initiation, propagation, and termination steps.
What is the environmental impact of burning alkanes?
Burning alkanes releases carbon dioxide (CO₂), a greenhouse gas that contributes to global warming, and can also release pollutants like carbon monoxide (CO) and nitrogen oxides (NOₓ).
How do alkanes react with hydrogen?
Alkanes do not typically react with hydrogen unless they are subjected to high pressure and temperature, in a process called hydrogenation (often used to convert alkenes to alkanes).
What is the relationship between the size of an alkane and its flammability?
Smaller alkanes (such as methane and propane) are more flammable than larger alkanes due to their lower boiling points and higher volatility.
How are alkanes used in the chemical industry?
Alkanes are used as fuels, solvents, and starting materials for the production of plastics, chemicals, and pharmaceuticals.
What is the formula of octane?
The formula of octane is C₈H₁₈.
What is the significance of methane (CH₄) in terms of energy production?
Methane is a key fuel in natural gas, used for electricity generation, heating, and as a raw material in the chemical industry.
