Formulae, Functional Groups & Terminology (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Chemistry): Flashcards
Exam code: 0654 & 0973
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What is a hydrocarbon?
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Cards in this collection (24)
What is a hydrocarbon?
A hydrocarbon is a compound that contains hydrogen and carbon atoms only. It does not contain any other elements.
A displayed formula shows all the ______ and all the ______ in a molecule.
A displayed formula shows all the atoms and all the bonds in a molecule.
What must be shown in a displayed formula that is not shown in a molecular formula?
A displayed formula shows the spatial arrangement of all atoms and all the bonds between them.
A molecular formula only shows the number and type of atoms, without indicating the bonds.
A student describes a hydrocarbon as a 'mixture of carbon and hydrogen molecules'. State two errors in this description.
Two errors:
Hydrocarbons are compounds (not mixtures)
They consist of carbon and hydrogen atoms (not molecules).
Hydrocarbons contain only carbon and hydrogen.
True or False?
Carbon dioxide and metal carbonates are classified as organic compounds because they contain carbon.
False.
By convention, carbon dioxide and metal carbonates are not classified as organic compounds, even though they contain carbon. Organic compounds are carbon-containing compounds excluding these exceptions.
State three types of formula that can be used to represent organic compounds.
Organic compounds can be represented using:
Displayed formula (showing all atoms and bonds)
Structural formula (showing the arrangement of groups)
General formula (showing the pattern common to a homologous series).
What is a homologous series?
A homologous series is a family of similar compounds with similar chemical properties. Members share the same general formula and display a trend in physical properties.
Alkanes have the functional group ______, alkenes have the functional group ______, and alcohols have the functional group ______.
Alkanes have the functional group C-C, alkenes have the functional group C=C, and alcohols have the functional group -OH.
How does the molecular formula change from one member to the next in a homologous series?
Each successive member of a homologous series differs from the previous one by one CH2 unit. This means the molecular formula increases by one carbon atom and two hydrogen atoms.
True or False?
Members of the same homologous series have the same general formula and display a gradual trend in physical properties.
True.
All members of a homologous series share the same general formula and the same functional group. Physical properties such as boiling point change gradually from one member to the next.
Why do members of the same homologous series have similar chemical properties?
Members of the same homologous series have similar chemical properties because they all contain the same functional group, which is the part of the molecule responsible for the characteristic reactions of that series.
Alcohols belong to a homologous series. Their names end in ______ and their functional group is the ______ group.
Alcohols belong to a homologous series. Their names end in -ol and their functional group is the -OH group.
What is a saturated compound?
A saturated compound is a molecule in which all carbon-carbon bonds are single bonds. Alkanes are examples of saturated compounds.
Unsaturated compounds contain one or more carbon-carbon ______ bonds. ______ are unsaturated compounds.
Unsaturated compounds contain one or more carbon-carbon double bonds. Alkenes are unsaturated compounds.
How can aqueous bromine be used to distinguish between a saturated and an unsaturated hydrocarbon?
When aqueous bromine is added, an unsaturated hydrocarbon (such as an alkene) decolourises the bromine water because it reacts via addition across the double bond. A saturated hydrocarbon (such as an alkane) does not react and the bromine water remains orange-brown.
True or False?
An alkane with four carbon atoms has the molecular formula C4H8.
False.
Alkanes follow the general formula CnH2n+2. With four carbons (n = 4), the formula is C4H10, not C4H8. C4H8 is the formula for an alkene (butene).
Why are alkanes described as saturated while alkenes are described as unsaturated?
Alkanes are saturated because all their carbon-carbon bonds are single bonds, so no more hydrogen atoms can be added.
Alkenes are unsaturated because they contain at least one carbon-carbon double bond, allowing addition reactions to occur.
Ethene has the molecular formula ______ and is the first member of the ______ homologous series.
Ethene has the molecular formula C2H4 and is the first member of the alkenes homologous series.
What does the stem of an organic compound's name indicate? For example, prop-.
The stem indicates the number of carbon atoms in the longest continuous carbon chain. For example, meth- = 1 carbon, eth- = 2 carbons, prop- = 3 carbons and but- = 4 carbons.
A compound with 3 carbons and a C=C double bond is named ______.
A compound with 4 carbons and only C-C single bonds is named ______.
A compound with 3 carbons and a C=C double bond is named propene.
A compound with 4 carbons and only C-C single bonds is named butane.
True or False?
But-1-ene and but-2-ene are the same compound, just named differently.
False.
But-1-ene and but-2-ene are different compounds. In but-1-ene the C=C double bond starts on the first carbon, while in but-2-ene it starts on the second carbon. The number indicates the position of the double bond.
Why is it necessary to include a number in the name but-1-ene but not in the name propene?
Propene has only one possible position for the C=C double bond, so no number is needed.
Butene has two possible positions (carbons 1 and 2), so a number is required to specify which carbon the double bond starts on.
The suffix ______ indicates an alkane, ______ indicates an alkene, and ______ indicates an alcohol.
The suffix -ane indicates an alkane, -ene indicates an alkene, and -ol indicates an alcohol.
Name the organic compound with the molecular formula C2H5OH.
What homologous series does it belong to?
The compound is ethanol.
It belongs to the alcohol homologous series, identified by the -ol suffix and the -OH functional group.
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