11 - Organic chemistry

Question 1

State the general formulae for alkanes, alkenes, alcohols, carboxylic acids, and esters

Answer 1

(1 for each of)
Alkanes: C_nH_2n+2
Alkenes: C_nH_2n
Alcohols: C_nH_2n+1OH
Carboxylic acids (and esters): C_nH_2n+1COOH

(cambridge wants C.A. formula but be careful about extra carbon)

Question 2

Define functional group

Answer 2

An atom/group of atoms (1 for each)
that determine the chemical properties for a homologous series (3)

Question 3

Define structural formula

Answer 3

An unambiguous description of the way the atoms in a molecules are arranged (5)

Question 4

Define structural isomer

Answer 4

Compounds with the same molecular formula (2)
but different structural formulae (2)
*Understand how bonds are written in a structural formulae; i.e. propene as CH₃CH=CH₂

(i.e. single bonds not shown but double bonds shown)

Question 5

Define homologous series

Answer 5

A group of similar compounds (1)
with similar chemical properties (2)
due to the presence of the same functional group (2)

Question 6

State the difference between a saturated and unsaturated compound

Answer 6

Saturated compounds are compounds in which all carbon-carbon bonds are single bonds (3)
Unsaturated compounds are compounds in which one or more carbon-carbon bonds are not single bonds (2)

Question 7

Describe the general characteristics of a homologous series

Answer 7

(Compounds in a homologous series)
- have the same functional group (1)
- have the same general formula (1)
- differ from one compound to the next by a -CH₂- unit (1)
- display a trend in physical properties (1)
- have similar chemical properties (1)

Question 8

Describe the chemical properties of alkanes

Answer 8

Generally unreactive (1)
except in terms of combustion (2)
and substitution by chlorine (2)

Question 9

Explain the cracking of large alkane molecules and why they are done

Answer 9

Long-chain alkane molecules are broken down via cracking into more useful. short-chain hydrocarbons (2)
using a high temperature and a nickel/platinum catalyst (2)
because short-chain hydrocarbons are more useful hydrocarbons (1)

Question 10

State the advantages and disadvantages of fermentation versus catalytic addition of steam to ethene

Answer 10

Fermentation: (1 for each)
- requires less energy
- is cheap
- uses renewable raw materials
- is labour intensive
- is time consuming
(or vice versa for catalytic addition of steam to ethene)