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HKDSE Chemistry > 26: Homologous Series, Structural Formulae and Naming of Carbon Compounds > Flashcards

26: Homologous Series, Structural Formulae and Naming of Carbon Compounds Flashcards

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1
Q

List 4 unique structural and bonding properties of carbon.

A
  1. Carbon, unlike most elements, has the ability to form structures with chains, branched chains, and rings of varying size.
  2. The C-C and C-H bonds in most carbon compounds are strong bonds with low polarities.
  3. Every carbon atoms has four outermost shell electrons. It can either form four single covalent bonds or different combinations of single bonds and multiple bonds.
  4. When carbon atoms from chains or rings containing only single covalent bonds, the electrons that are not being used to bond carbon atoms together can be used to bond with atoms of other elements such as hydrogen, oxygen, nitrogen, or halogens.
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2
Q

What is the empirical formula?

A

The empirical formula tells the simplest whole number ratio of the atoms of each element in a compound.

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3
Q

What is the empirical formula of alkenes?

A

CH2

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4
Q

What is the molecular formula?

A

The molecular formula shows the total number of atoms of each element present in one molecule of a compound.

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5
Q

What is the structural formula?

A

The structural formula of a compound shows how the atoms are bonded together.

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6
Q

What is the condensed structural formula?

A

The condensed structural formula shows the unique arrangement of atoms in a molecules of a compound without directly showing all bonds.

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7
Q

What are the rules for writing condensed structural formulas?

A
  1. Each carbon atoms is written separately with the atoms or groups of atoms attached to it.
  2. Carbon-carbon multiple bonds must be shown.
  3. Branches in the main carbon chain are shown in brackets.
  4. Repeating groups of atoms can be placed in a bracket with a subscript to show how many times it is repeated.
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8
Q

What is the skeletal formula?

A

The skeletal formula is a simplified version of the structural formula, it is a zig-zag line where each vertex represents a carbon atom with as many hydrogen atoms as needed. Any hydrogen atom not attached to a carbon atom of any atom other than hydrogen or carbon must be shown.

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9
Q

What is the chemical equation when sodium reacts with alcohols (ROH)?

A

2ROH + 2Na -> 2RONa + H2

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10
Q

What is a functional group?

A

A functional group is either a single atom or a group of atoms which determines most of the properties of a compound.

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11
Q

What is a homologous series?

A

A homologous series is a family of compounds having a common functional group, with each successive member differing by a -CH2- unit.

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12
Q

What is the name of the functional group of alkenes?

A

Carbon-carbon double bond

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13
Q

What is the name of the functional group of alkanols?

A

Hydroxyl group

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14
Q

What is the name of the functional group of alkanoic acids?

A

Carboxyl group

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15
Q

What is the name of the homologous series having functional group with formula C=C?

A

Alkenes

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16
Q

What is the scientific name of the homologous series having functional group with formula -O-H?

A

Alkanols

17
Q

What is the common name of the homologous series having functional group with formula -O-H?

A

Alcohols

18
Q

What is the scientific name of the homologous series having functional group with formula -COOH?

A

Alkanoic acids

19
Q

What is the common name of the homologous series having functional group with formula -COOH?

A

Carboxylic acids

20
Q

What is the functional group of alkanes?

A

They have no functional group, since they only consist of C-C and C-H bonds, which are present in most other organic compounds.

21
Q

What are the characteristics shown by the members in a homologous series?

A
  1. They have the same general formula.
  2. Each member differs from the next by a -CH2- unit.
  3. They have similar chemical properties.
  4. Their physical properties show a gradation / gradual change from one member to the next.
22
Q

What are the rules of punctuation when naming carbon compounds using IUPAC naming?

A

A comma (,) is used between two numbers.
A hyphen (-) is used between a number and a letter.
The name should have no space and should be one word throughout.

23
Q

What are the rules when naming branched-chain alkanes using IUPAC naming?

A
  1. Take the longest continuous chain (or the chain with the most branches of carbon atoms as the parent chain.
  2. Identify the alkyl group(s) attached to the parent chain.
  3. Number the alkyl group(s) attached by counting from the end nearest to the alkyl groups, thus minimising the numbers given to the groups.
  4. Name the compound using the name of the parent chain, prefixed by the alkyl groups and their numbers. Arrange the alkyl groups alphabetically.
  5. Add prefixes such as “di”, “tri”, “tetra”, to indicate multiple copies of the same alkyl group.
    format: (number)-(branch)(parent chain alkane)
24
Q

What are the rules when naming alkenes using IUPAC naming?

A
  1. Take the longest continuous chain containing the double bond as the parent chain.
  2. For an alkene with 4 or more carbon atoms in the parent chain, assign a number to the double bond counting from the end nearest to the first carbon atom forming double bond.
  3. If there are any branches, name them according to the numbers assigned previously.
    format: (number)-(branch)(parent chain alkane prefix)-(location of double bond)-ene
25
Q

What are the rules when naming alkanols using IUPAC naming?

A
  1. Take the longest continuous chain containing the hydroxyl group as the parent chain.
  2. Assign a number to the hydroxyl group counting from the end nearest to the carbon atom bonded to the group.
  3. If there are any branches, name them according to the numbers assigned previously.
  4. If there are more than one hydroxyl group, add the last letter “e” in the name of the corresponding alkane parent chain.
    format: (number)-(branch)(parent chain alkane)-(location of hydroxyl group)-ol
26
Q

What are the rules when naming alkanoic acids using IUPAC naming?

A
  1. Take the longest continuous chain containing all carboxyl groups as the parent chain.
  2. Assign number 1 to the carbon atom of the carboxyl group.
  3. If there are any branches, name them according to the numbers assigned previously.
  4. If there are two carboxyl groups, add the suffix -dioic acid to the name of the corresponding alkane.
    format: (number)-(branch)(parent chain alkane prefix)-(oic acid / dioic acid)
27
Q

What is the shortest straight-chain alkane that is a liquid at room temperature?

A

Pentane

28
Q

What is the trend in the melting and boiling points of straight-chain alkanes and why?

A

As the carbon chain length increases, the melting and boiling points increase, since the molecular size and the number of electrons per molecule increase and the larger molecules experience stronger van der Waals’ forces.

29
Q

What is the solubility of alkanes in water?

A

Alkanes are insoluble in water, because water molecules are held together by hydrogen bonds which are much stronger than the van der Waals’ forces that act between alkane molecules and water molecules.

30
Q

How can a mixture of alkanes and water be separated?

A

By using a separating funnel.

31
Q

What is the solubility of alcohols in water?

A

Methanol and ethanol are completely miscible with water. The solubility of alcohols decreases as the molecular size increases, until hexan-1-ol which is completely insoluble in water. This is because the water insoluble part bonded to the water soluble hydroxyl group gets larger, making larger alcohols less soluble in water.

32
Q

What is the density of alkanes when compared with water?

A

Alkanes are less dense than water, when mixed with water, they form two immiscible layers with the alkanes at the top layer.

HKDSE Chemistry (28 decks)

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