Alkanes Flashcards
What is the formula for an Alkane?
CnH2n+2
What is the trend in boiling points of straight chain alkanes?
Increases
- as chain length increases so does surface area contact
- stronger VDW forces between molecules
What is crude oil?
a mixture consisting of mainly alkanes
What is distillation?
method that separates mixture os miscible liquids
separation is based on boiling points
What happens during distillation in a tower?
- 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
What is a fraction?
mixture of hydrocarbons with similar boiling points
Why does the boiling point of alkanes increase?
increased mr
increased surface area contact
How do properties of hydrocarbons change as the chain gets longer?
- more viscous
- harder to ignite
- less volatile
- higher boiling point and stronger VDW
Why are hydrocarbons cracked?
to make use of larger hydrocarbons
shorter chains are higher in demand
alkanes make plastics and polymers
What is cracking?
breaking if longer chain alkane molecules into small ones
involves breaking of strong C-C covalent bonds
What are the conditions of Thermal cracking?
high temperature
high pressure
What dies thermal cracking form?
high % of alkENES and straight chain alkanes
What are the conditions of Catalytic Cracking?
high temperature
moderate pressure
ZEOLITE as catalyst
What is formed from Catalytic Cracking?
motor fuels
aromatic hydrocarbons
cycloalkanes
What is complete combustion
alkane and excess oxygen reacting with CO2
What is the equation for complete combustion
alkane + oxygen > carbon dioxide + water
What is incomplete combustion?
when there is a limited supply if oxygen
What is formed in incomplete combustion?
carbon monoxide OR carbon
What is flue gas desulfurisation?
removes SO2 from the gases emitted from fossil-fuel power plants
Which bases neutralise SO2 (sulfur dioxide )
CaO or CaCO3
What is the equation for the neutralisation of SO2 with CaO?
CaO(s) + SO2(g) > CaSO3(s)
What causes the production of Nitrogen Oxides?
high temperatures in engines cause nitrogen and oxygen to react
What is the equation for the reaction if O2 and N2?
N2(g) + O2(g) > 2NO(g)
What is the function of a catalytic converter?
to reduce the amount of CO and NO released by engines
Why does a catalytic converter have a honeycomb structure?
increases the surface area and it is cost effective
its thinly coated in metal catalyst platinum/rhodium/palladium
Why is a catalytic converter made of ceramic material
to withstand high temperatures inside the combustion engine
How does the catalytic converter work?
dangerous polluting gases pass over the catalyst and react with each other to produce less harmful gases
