C9 - Crude Oils & Fuels

Question 1

What is a hydrocarbon?

Answer 1

molecules only containing H & C

Question 2

What is crude oil?

Answer 2

mixture of diff. hydrocarbons @ diff. lengths

Question 3

Define alkane.

Answer 3

saturated hydrocarbons (single cov. bond btwn carbons) ending in -ane

Question 4

What is the general formula of an alkane?

Answer 4

Cn H2n+2

Question 5

What are the prefixes for the first 4 hydrocarbons?

Answer 5

me-
eth-
prop-
but-

Question 6

Define viscosity.

Answer 6

how thick a liquid is

Question 7

How does chain length affect the viscosity of hydrocarbons?

Answer 7

long chain length = high viscosity (thick/gloopy)
short chain length = low viscosity (runny/thin)

Question 8

Define flammability.

Answer 8

how easily something can catch on fire

Question 9

How does chain length affect the flammability of hydrocarbons?

Answer 9

long chain length = less flammable
short chain length = v flammable

Question 10

Define boiling point.

Answer 10

temp which liquid -> gas

Question 11

How does chain length affect the boiling point of hydrocarbons?

Answer 11

long chain length = high BP
short chain length = low BP

Question 12

What holds hydrocarbons together?

Answer 12

weak intermolecular forces

Question 13

How many bonds can a carbon atom form?

Answer 13

4 covalent bonds

Question 14

How do hydrocarbon fuels release energy?

Answer 14

by combustion

Question 15

What is complete combustion?

Answer 15

carbon & hydrogen atoms react with O2 in combustion & bcm oxidised
if oxygen is unlimited, reaction -> CO2 + H2O

Question 16

How can be break down long chain hydrocarbons, into smaller more useful hydrocarbons?

Answer 16

cracking

Question 17

What are short chain hydrocarbons mostly used for?

Answer 17

fuels

Question 18

Other than short chain hydrocarbons, what else is produced in cracking?

Answer 18

alkenes

Question 19

What is needed in catalytic cracking?

Answer 19

high temp. & catalyst

Question 20

What is needed in thermal cracking?

Answer 20

high temp. & steam

Question 21

What is the functional group of alkenes?

Answer 21

C=C (double bond, 2 carbons atms)

Question 22

Which is more reactive, alkenes or alkanes?

Answer 22

alkenes

Question 23

What is the test for alkenes? What signifies a positive result?

Answer 23

add bromine water
+ = orange -> colourless

Question 24

How are crude oils formed?

Answer 24

Crude oil is a finite resource that is found in the Earth’s crust. It is the remains of organisms that lived and died millions of years ago - mainly plankton which was buried in mud

Question 25

what is the process of fractional distillation?

Answer 25

crude oil is heated until most hydrocarbons are gases
gases enter colum, which has a temp gradient
vapours move up columns & condense at their boiling points
longer hydrocarbons have higher boiling points & shorter hydrocarbons have lower boiling points
so hydrocarbons are seperated on length