2. Hydrocarbons- alkanes, alkene, alkynes

Question 1

what is the main source of hydrocarbons.

Answer 1

Crude oil

Question 2

Hydrocarbons are

Answer 2

compounds containing carbon and hydrogen only

Question 3

Hydrocarbons provide us with

Answer 3

fuels such as petrol, diesel and kerosene

Question 4

Hydrocarbons are also the starting compounds we use to

Answer 4

make many new compounds, such as most of the plastics we meet in everyday life.

Question 5

Crude oil is extracted from

Answer 5

porous seams of rock found beneath an impervious layer of rock within the Earth’s crust

Question 6

General formula of alkanes

Answer 6

CnH2n+2

Question 7

Alkanes are unreactive towards most chemical reagents because

Answer 7

there is only a very small electronegativity difference between carbon and hydrogen

Question 8

Alkanes are essentially non-polar so there are

Answer 8

no areas of higher or lower electron density that can be attacked by reagents such as acids and alkalis

Question 9

The majority of compounds found in the mixture of

hydrocarbons we call crude oil are

Answer 9

alkanes

Question 10

the molecular formula of pentane

Answer 10

C5H12

Question 11

the simplest class of hydrocarbons

Answer 11

only contain single bonds between carbon atoms

alkanes

Question 12

saturated hydrocarbons are

Answer 12

hydrocarbons that contain only single bonds between carbon atoms.

They are called saturated because each carbon atom is bonded to as many hydrogen atoms as possible (bonded to four other atoms )
In other words, the carbon atoms are saturated with hydrogen

Question 13

alkanes are called saturated because

Answer 13

each carbon atom is bonded to as many hydrogen atoms as possible (bonded to four other atoms )

In other words, the carbon atoms are saturated with hydrogen

Question 14

saturated implies that

Answer 14

no carbon-carbon multiple bonds exist in these organic compounds

Question 15

Crude oil is found where

Answer 15

trapped in layers of rock beneath the surface of the Earth.

Question 16

Crude oil is a

Answer 16

complex mixture of hydrocarbons – alkanes, cycloalkanes and aromatic compounds

Question 17

Cycloalkanes are

Answer 17

saturated hydrocarbons in which there is a ‘ring’ consisting of three or more carbon atoms.

Question 18

a cycloalkane does not follow the general alkane formula, CnH2n + 2. because

Answer 18

the two end carbon atoms in an alkane chain bond to each other, forming a closed ring.

Therefore there are two fewer hydrogen atoms in a cycloalkane compared with its equivalent straight chain alkane

Question 19

why are there fewer hydrogen atoms in a cycloalkane compared with its equivalent straight chain alkane

Answer 19

because the two end carbon atoms in an alkane chain bond to each other, forming a closed ring

Question 20

Another class of hydrocarbons called aromatic hydrocarbons, which are also known as arenes, are based on

Answer 20

hexagonal benzene rings