Alkanes

Question 1

What is the formula for an Alkane?

Answer 1

CnH2n+2

Question 2

What is the trend in boiling points of straight chain alkanes?

Answer 2

Increases
- as chain length increases so does surface area contact
- stronger VDW forces between molecules

Question 3

What is crude oil?

Answer 3

a mixture consisting of mainly alkanes

Question 4

What is distillation?

Answer 4

method that separates mixture os miscible liquids
separation is based on boiling points

Question 5

What happens during distillation in a tower?

Answer 5

• crude oil vapourised
• passes tower which is hot at the bottom and cool at the top
• vapouring rises and cools
• molecules condense at different heights due to different boiling pts
• higher boiling point= condenses further doen coloumn
• produces fractions

Question 6

What is a fraction?

Answer 6

mixture of hydrocarbons with similar boiling points

Question 7

Why does the boiling point of alkanes increase?

Answer 7

increased mr
increased surface area contact

Question 8

How do properties of hydrocarbons change as the chain gets longer?

Answer 8

• more viscous
• harder to ignite
• less volatile
• higher boiling point and stronger VDW

Question 9

Why are hydrocarbons cracked?

Answer 9

to make use of larger hydrocarbons
shorter chains are higher in demand
alkanes make plastics and polymers

Question 10

What is cracking?

Answer 10

breaking if longer chain alkane molecules into small ones
involves breaking of strong C-C covalent bonds

Question 11

What are the conditions of Thermal cracking?

Answer 11

high temperature
high pressure

Question 12

What dies thermal cracking form?

Answer 12

high % of alkENES and straight chain alkanes

Question 13

What are the conditions of Catalytic Cracking?

Answer 13

high temperature
moderate pressure
ZEOLITE as catalyst

Question 14

What is formed from Catalytic Cracking?

Answer 14

motor fuels
aromatic hydrocarbons
cycloalkanes

Question 15

What is complete combustion

Answer 15

alkane and excess oxygen reacting with CO2

Question 16

What is the equation for complete combustion

Answer 16

alkane + oxygen > carbon dioxide + water

Question 17

What is incomplete combustion?

Answer 17

when there is a limited supply if oxygen

Question 18

What is formed in incomplete combustion?

Answer 18

carbon monoxide OR carbon

Question 19

What is flue gas desulfurisation?

Answer 19

removes SO2 from the gases emitted from fossil-fuel power plants

Question 20

Which bases neutralise SO2 (sulfur dioxide )

Answer 20

CaO or CaCO3

Question 21

What is the equation for the neutralisation of SO2 with CaO?

Answer 21

CaO(s) + SO2(g) > CaSO3(s)

Question 22

What causes the production of Nitrogen Oxides?

Answer 22

high temperatures in engines cause nitrogen and oxygen to react

Question 23

What is the equation for the reaction if O2 and N2?

Answer 23

N2(g) + O2(g) > 2NO(g)

Question 24

What is the function of a catalytic converter?

Answer 24

to reduce the amount of CO and NO released by engines

Question 25

Why does a catalytic converter have a honeycomb structure?

Answer 25

increases the surface area and it is cost effective

its thinly coated in metal catalyst platinum/rhodium/palladium

Question 26

Why is a catalytic converter made of ceramic material

Answer 26

to withstand high temperatures inside the combustion engine

Question 27

How does the catalytic converter work?

Answer 27

dangerous polluting gases pass over the catalyst and react with each other to produce less harmful gases