Alkanes (Edexcel IGCSE Chemistry (Modular): Unit 1): Flashcards
Exam code: 4XCH1
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- FrontWhat are Alkanes?
Define saturated (as used for hydrocarbons).
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Cards in this collection (15)
Define saturated (as used for hydrocarbons).
A saturated hydrocarbon contains only single carbon-carbon bonds — there are no double bonds between carbon atoms.
Alkanes belong to a group of .......... hydrocarbons, meaning they have only .......... carbon-carbon bonds.
Alkanes belong to a group of saturated hydrocarbons, meaning they have only single carbon-carbon bonds.
Why are alkanes described as saturated?
Alkanes are described as saturated because they contain only single carbon-carbon bonds. There are no double bonds between carbon atoms, so the molecule cannot take on any more hydrogen atoms.
True or False?
Pentane has the molecular formula C5H12.
True.
Pentane is the fifth alkane. Using the general formula CnH2n+2 with n = 5 gives C5H12.
What types of reactions can alkanes undergo?
Alkanes can undergo combustion, can be cracked into smaller molecules, and can react with halogens in the presence of light.
Complete the table of alkane molecular formulas.
Name
Molecular formula
Methane
Ethane
Propane
Butane
Pentane
Complete the table of alkane molecular formulas.
Name
Molecular formula
Methane
CH4
Ethane
C2H6
Propane
C3H8
Butane
C4H10
Pentane
C5H12
True or False?
Alkanes are highly reactive compounds.
False.
Alkanes are generally unreactive compounds, though they do undergo combustion, cracking, and reactions with halogens.
What is the main component of natural gas?
The main component of natural gas is methane, the simplest alkane with the molecular formula CH4.
What is a substitution reaction?
A substitution reaction is one in which one atom is swapped (replaced) with another atom.
What conditions are needed for alkanes to react with halogens?
Alkanes react with halogens in the presence of ultraviolet (UV) radiation. Without UV light, this substitution reaction does not occur.
In the presence of UV radiation, methane reacts with bromine to form .......... and ...........
In the presence of UV radiation, methane reacts with bromine to form bromomethane and hydrogen bromide.
True or False?
Alkanes react with halogens in the dark.
False.
Alkanes only react with halogens in the presence of ultraviolet (UV) radiation. The reaction does not occur in the dark.
What type of compounds are formed when alkanes react with halogens?
The products are called halogenoalkanes (or haloalkanes). These are compounds in which one or more hydrogen atoms of the alkane have been replaced by a halogen atom.
True or False?
Chlorine can react with methane in the presence of UV light to form chloromethane.
True.
Methane reacts with chlorine under UV light in a substitution reaction, producing chloromethane and hydrogen chloride.
What are halogenoalkanes used for?
Halogenoalkanes are used as solvents, refrigerants, propellants, and pharmaceuticals.
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