Organic Chemistry (topic 7) Flashcards
What are hydrocarbons?
Hydrocarbons are molecules ONLY up of carbon & hydrogen atoms.
What are the first 4 alkanes?
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
What is the formula for ALKANES
CnH2n+2 ( multiply the carbon by 2 then add 2)
What properties change as the length of hydrocarbon chains change?
Viscosity ( how thicc it is)
Flammability ( how quickly it combusts / burns)
Boiling point (the temperature at which liquid turns to gas)
State properties of LONG chain hydrocarbons
1) EXTREMELY viscous (thicc)
2) high boiling point
3) less flammable
State properties of SHORT chain hydrocarbons
1) high boiling points
2) extremely flammable
3) less viscous
What happens when hydrocarbons combust completely?
Carbon & hydrogen atoms react with oxygen and become oxidised, they then combust and release ENERGY.
Unlimited oxygen makes the reaction completely combust which produces 2 waste products; carbon dioxide & water .
You have to give a balanced equation for completely combusted hydrocarbons
What is crude oil?
A mixture of molecules called hydrocarbons, each hydrocarbon has a different boiling point.
They are also a type of fossil fuel (finite)
Why is fractional distillation used for in crude oil?
It separates the crude oil into fractions, these fractions contain hydrocarbons with Similar boiling points. We do this so we can use the crude oil for fuel or feedstock [solvents , lubricants, detergents]
Explain the fractional distillation process for crude oil.
The crude oil is heated at high temperatures until the hydrocarbons boil into gases inside of a fractional column.
The column has a temperature gradient with the bottom being the hottest, this means that the long chain hydrocarbons [high boiling point], will condense & drain out early on. The short chain hydrocarbons [low boiling point] condense & drain out near the top .
At the end you will have crude oil separated into different fractions with similar boiling points
2 ways to carry out cracking:
Catalytic: High temperatures and adding a catalyst to your reaction
Steam: high temperatures and steam
What happens when you crack hydrocarbons?
They turn into alkENEs
How to test for alkENES?
Shake bromine water with suspected alkene, if the solution turns colourless then alkene is present.
AlkENES have 2 covalent bonds
