Alkanes Flashcards
What is the general formula for alkanes
CnH2n+2
Are alkanes saturated or unsaturated
Saturated as they only contain single bonds
What is the general formula for cycloalkanes
Cnh2n
How to carry out fractional distillation
Crude oil is vaporised at 350 degrees
Goes through a fractionating column and as it goes up it gets cooler.
Due to the alkane molecules different chain lengths, they have different boiling points so each fraction condenses at a different temperature
Hydrocarbons with the lowest boiling point do not condense, they’re drawn off as gases at the bottom
Why are fractions cracked
To make them into more useful smaller molecules
What is cracking
Breaking long chained alkanes into smaller hydrocarbons by breaking the c-c bonds
Describe thermal cracking
High temp up to 1000 degrees, High pressure up to 70 atm
Produces alkenes which are used to make valuable products like polymers
Describe catalytic cracking
Uses Zeolite catalyst at slight pressure and high temp around 450 degrees
Produces aromatic hydrocarbons and motor fuels
Catalysts cut costs by using slight pressure and saves time
What are the products of combustion
Water and carbon dioxide
What is incomplete combustion
When there is not enough oxygen so the products are carbon monoxide and water
Can also form carbon soot which can cause breathing problems
What happens when engines dont burn all of the fuel molecules
They make unburnt hydrocarbons
How are oxides of nitrogen produces
High pressure and temp of a car engine causes the particles from the air to react together
When to hydrocarbons and nitrogen oxides react
In the prescence of sunlight to form ground level ozone which is a component of smog
What forms when Sulphur is burnt
Sulfur dioxide gas
How is sulfur dioxide gas converted into acids rain
In the atmosphere it dissolve in the moisture and gets converted into sulphuric acid and then acid rain
