Introduction (Edexcel IGCSE Science (Double Award): Chemistry): Flashcards
Exam code: 4SD0
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- FrontOrganic Compounds
Define hydrocarbon.
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Cards in this collection (27)
Define hydrocarbon.
A hydrocarbon is a compound containing carbon and hydrogen atoms only.
The empirical formula shows the .......... of atoms in a molecule, while the molecular formula shows the .......... of atoms.
The empirical formula shows the simplest whole-number ratio of atoms in a molecule, while the molecular formula shows the actual number of atoms.
True or False?
Carbon dioxide is classified as an organic compound.
False.
By convention, carbon dioxide (and carbon monoxide and metal carbonates) are not classified as organic compounds, even though they contain carbon.
What does a displayed formula show that a structural formula does not?
A displayed formula shows every atom and every bond in the molecule. A structural formula omits most covalent bonds and only shows key bonds such as double bonds.
Define homologous series.
A homologous series is a family of organic compounds that share the same functional group, the same general formula, similar chemical properties and a gradation in physical properties. Each member differs from the next by CH2.
Isomers are compounds that have the same .......... formula but different .......... formulae.
Isomers are compounds that have the same molecular formula but different displayed formulae.
Define functional group.
A functional group is a group of atoms bonded in a specific arrangement that determines the chemical properties of the homologous series it belongs to.
True or False?
All members of a homologous series have the same general formula.
True.
All members share the same general formula, the same functional group and similar chemical properties, with each successive member differing by CH2.
What is the general formula for the alkane homologous series?
The general formula for alkanes is CnH2n+2, where n is the number of carbon atoms in the chain.
Define prefix (organic naming).
A prefix (or stem) in an organic compound's name indicates the number of carbon atoms in the longest continuous carbon chain: meth- (1), eth- (2), prop- (3), but- (4), pent- (5) and hex- (6).
In IUPAC naming, the .......... tells you the number of carbon atoms, and the .......... tells you the functional group present.
In IUPAC naming, the prefix (stem) tells you the number of carbon atoms, and the suffix tells you the functional group present.
What is the IUPAC name for a straight-chain alkane with four carbon atoms?
The name is butane. The prefix but- indicates four carbon atoms and the suffix -ane shows it belongs to the alkane family (no functional group other than single C–C bonds).
True or False?
The suffix -anol indicates that a compound belongs to the alcohol family and contains an –OH functional group.
True.
The -anol suffix (e.g. ethanol, propanol) indicates the compound is an alcohol with an –OH functional group attached to the carbon chain.
A compound named prop.......... contains three carbon atoms and a C=C double bond.
A compound named propene contains three carbon atoms and a C=C double bond.
What does the prefix di- indicate in an organic compound name?
The prefix di- indicates that two of the same functional group are present in the molecule.
True or False?
Propene contains two carbon atoms.
False.
Propene contains three carbon atoms. The prefix prop- always means three carbons. The suffix -ene indicates that propene contains a C=C double bond and belongs to the alkene homologous series.
How do you name the position isomers of an unbranched alkene?
Position isomers of an unbranched alkene are named by placing a number before the suffix -ene to show the carbon where the double bond starts. For example, but-1-ene has the double bond starting on carbon 1, while but-2-ene has it starting on carbon 2.
Define IUPAC nomenclature.
IUPAC nomenclature is the internationally agreed system for naming organic compounds, using a prefix to show chain length and a suffix to show the functional group.
Define addition reaction.
An addition reaction is one in which two or more molecules combine to form a single larger molecule with no other products.
In a substitution reaction, one .......... is replaced by another, whereas in an addition reaction, molecules combine to form a .......... with no other products.
In a substitution reaction, one atom (or group of atoms) is replaced by another, whereas in an addition reaction, molecules combine to form a single larger molecule with no other products.
True or False?
The reaction of ethene with bromine is classified as an addition reaction.
True.
Bromine adds across the double bond of ethene to form dibromoethane (C2H4Br2) with no other products, which is the defining feature of an addition reaction.
What are the three reaction types used to classify reactions of organic compounds at IGCSE?
The three types are substitution, addition and combustion.
Define substitution reaction.
A substitution reaction is one in which one functional group (or atom) is replaced by another, leaving the carbon skeleton unchanged.
True or False?
Knowledge of reaction mechanisms is required to classify organic reactions for this specification.
False.
The specification explicitly states that knowledge of reaction mechanisms is not required. Students only need to classify reactions as substitution, addition or combustion.
Methane reacts with bromine under ultraviolet light. What type of reaction is this and what are the products?
This is a substitution reaction. One hydrogen atom is replaced by bromine, giving bromomethane (CH3Br) and hydrogen bromide (HBr) as products.
Complete combustion of a hydrocarbon requires .......... oxygen and produces .......... and water as the only products.
Complete combustion of a hydrocarbon requires excess oxygen and produces carbon dioxide and water as the only products.
How does incomplete combustion of a hydrocarbon differ from complete combustion in terms of products?
Incomplete combustion occurs when oxygen supply is limited. Instead of carbon dioxide, the products include carbon monoxide (and possibly soot/unburned carbon). Water is produced in both cases.
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