C4 Crude Oil

Question 1

define hydrocarbon

Answer 1

a compound containing hydrogen and carbon ONLY

Question 2

define saturated

Answer 2

containing single bonds only

Question 3

define unsaturated

Answer 3

containing double / triple bonds

Question 4

define homologous series

Answer 4

a group of hydrocarbons represented by the same general formula

Question 5

define general formula

Answer 5

a formula which represents a homologous series e.g. the alkanes

Question 6

example of the molecular formula of an alkane

Answer 6

CH4 - C2H6 - C3H8

Question 7

Formula for the molecular formula of an alkane

Answer 7

CnH2n+2

Question 8

example of a displayed formula

Answer 8

H H H
H C H H C C H
H H H

Question 9

First 10 alkanes

Answer 9

1. methane
2. ethane
3. propane
4. butane
5. pentane
6. hexane
7. heptane
8. octane
9. nonane
10. decane

Question 10

what is a structural formula example

Answer 10

CH3CH3 - CH3CH2CH3

Question 11

How are alkanes of of different chain lengths that have different boiling points seperated

Answer 11

fractional distilllation

Question 12

what happens when you react bromide with methane in the presence of uv light

Answer 12

a broomethane is formed
called a substitution reaction
CH4 + Br2 -> CH3Br + HBr

Question 13

explain how alkanes are part of the homologous series

Answer 13

differ by -CH2 each time

contain the same functional group

Question 14

define functional group

Answer 14

a group of atoms which determine the reactivity of a homologous series
- display a gradual trend in physical properties e.g. as chain length increases, boiling point increases

Question 15

dine molecular formular

Answer 15

the actual number of atoms each element in a compound e.g. glucose - C6H12O6

Question 16

what is the empirical formula

Answer 16

the simplest whole number ratio of atoms of each element in a compound. e.g. glucose - CH20

Question 17

What happens when the chain length increases of hydrocarbons

Answer 17

• boiling point increase
• volatility decreases
• viscosity increases
• flammability decreases

Question 18

define volatility

Answer 18

the tendency to turn into a gas

Question 19

define viscosity

Answer 19

how easily it flows, thickness

Question 20

what is a fraction

Answer 20

a group of hydrocarbons with similar boiling points (i.e. similar chain lengths)

Question 21

how is crude oil separated into fractions

Answer 21

FRACTIONAL DISTILLATION - the gaseous fractions will condense into liquids at different temperatures depending on their boiling points

Question 22

explain the process of fractional distillation using correct vocab

Answer 22

• crude oil is fed into bottom of distillation tower and VAPORISED
• the tower is hot at bottom and cooler at top so there is a TEMPERATURE GRADIENT
• crude oil vapours CONDENSE into fractions according to their BOILING POINTS
• LONG CHAIN HYDROCARBONS HAVE HIGH BOILING POINTS and condense near bottom
• SHORT CHAIN HYDROCARBONS HAVVE LOW BOILING POINTS and condense near the top

Question 23

define combustion

Answer 23

the burning of fuel in o2

Question 24

what happens when hydrocarbons burn in the air when there is a plentiful supply of o2

Answer 24

release energy 
complete combustion 
produces co2 and h2o  
C3H8 + 5O2 ---> 3CO2 +4H2O
hydrogen and carbon are completely oxidised - now oxides

Question 25

what happens when hydrocarbons burn in the air when there is a limited supply of o2

Answer 25

INCOMPLETE COMBUSTION
carbon monoxide and carbon may also be formed
C3H8 +3 1/2O2 -> 3CO + 4H2O