F322: Basic Concepts And Alkanes

Question 0

Molecular formula

Answer 0

Actual number of atoms of each element in a compound

Question 1

Empirical formula

Answer 1

Simplest whole number ratio of atoms of each element in a compound

Question 2

Homologous series

Answer 2

A series of organic compounds with the same functional group but with each successive member differing by a CH2 group. (Thus they have the same general formula, show trends in physical properties eg. Boiling points, and have similar chemical properties)

Question 3

General formula

Answer 3

Simplest algebraic formula of a homologous series (eg. CnH2n+2 for alkanes)

Question 4

Structural formula

Answer 4

Minimal detail showing the arrangement of atoms in a molecule

Question 5

Displayed formula

Answer 5

The relative positioning of atoms and the bonds between them

Question 6

Skeletal formula

Answer 6

The simplified organic formula, showing only the carbon skeleton with associated functional groups

Question 7

Functional group

Answer 7

A group of atoms responsible for the characteristic reactions of a compound

Question 8

Structural isomer

Answer 8

Compounds with the same molecular formula but different structural formula

Question 9

Stereoisomer

Answer 9

Compounds with the same structural formula but a different arrangement of atoms in space

Question 10

E/Z isomerism

Answer 10

An example of stereoisomerism, restricted rotation about a C=C bond and two different groups attached to each of the carbon atoms. Z= groups with the higher Mr on the same side.

Question 11

Cis-Trans isomerism

Answer 11

A special case of E/Z, in which two of the constituent groups are the same. Z (cis) where the groups are on the same side, E (trans) where the groups are on opposite sides.

Question 12

(Free) Radical

Answer 12

A species with an unpaired electron (diradical- a species with 2 unpaired electrons)

Question 13

Bond fission

Answer 13

Bond breaking

Question 14

Homolytic fission

Answer 14

Bond breaks symmetrically, one bonding electron going to each atom, to form two radicals

Question 15

Heterolytic fission

Answer 15

Bond breaks asymmetrically, both electrons from the bond going to one atom, often forming a cation and an anion

Question 16

Curly arrow

Answer 16

Movement of an electron pair to show either breaking or making of a covalent bond (should start from from a bond or lone pair of electrons)

Question 17

Percentage yield

Answer 17

(Actual amount of product obtained/theoretical amount of product expected) X 100. Can be calculated with either moles or mass. Non 100% yields could occur due to: competing side reactions, some product could be lost when it is transferred, a reversable reaction has not had chance to reach equilibrium.

Question 18

Atom economy

Answer 18

(Molecular mass of desired product/sum of molecular masses of all products) X 100. High atom economy needed in industry to reduce waste and conserve finite resources.

Question 19

Hydrocarbon

Answer 19

A compound that contains carbon and hydrogen ONLY

Question 20

Crude oil

Answer 20

Fossil fuel, a mixture of hydrocarbons with different boiling points. A non-renewable resource that takes millions of years to form.

Question 21

Fractional distillation

Answer 21

A technique for separation on the basis of differences in boiling points

Question 22

Alkanes

Answer 22

Saturated (single bonds only) hydrocarbons. Tetrahedral shape around each carbon centre with a bond angle of 109.5 degrees.

Question 23

Trend in boiling points of Alkanes

Answer 23

Boiling points increase with increasing chain length and decrease with increased branching. (More electrons (longer branches) -> stronger and more frequent VDW, more energy needed to break intermolecular forces. More branches -> reduced surface CONTACT area, fewer VDW, less energy needed to break intermolecular forces.)

Question 24

Complete combustion of hydrocarbons

Answer 24

Burning in plentiful supply of oxygen -> CO2 + H2O (carbon dioxide is a greenhouse gas and increased levels of it in the atmosphere is leading to global warming)

Question 25

Incomplete combustion of hydrocarbons

Answer 25

Burning in a limited supply of oxygen -> CO (toxic) + H2O (yellow flame, black smoke)

Question 26

Cracking

Answer 26

Breaking by heat (thermal decomposition) of a long chained alkane into smaller alkanes (which combust more efficiently) and an alkene (used to make polymers and alcohols) any C-C bond can break, giving a mixture of products.

Question 27

Isomerisation

Answer 27

Converts straight chained hydrocarbons into branched chains (which combust more efficiently)

Question 28

Reforming

Answer 28

Converts straight chained hydrocarbons into ring compounds (cycloalkanes) + H2

Question 29

Substitution

Answer 29

When an atom or group of atoms is replaced by another atom or group of atoms

Question 30

Radical substitution

Answer 30

Alkane + halogen -> halogenoalkane + hydrogen halide.

Mechanism: initiation (homolytic fission by UV), propagation steps, termination.

Question 31

Condensation polymerisation

Answer 31

Loss of small molecule (usually H2O) from the reacting monomers.

Question 32

Hydrolysis

Answer 32

Splitting with water

Question 33

Elimination

Answer 33

1 reactant -> 2 products