Organic Chemistry Flashcards
What is a hydrocarbon compound
A compound consisting if hydrogen and carbon only
What does the term fraction mean
A fraction is each liquid collected after a mixture is put through the process of fractional distillation
As the length of a hydrocarbon increases and it’s physical properties (boiling point, viscosity, flammability)
Longer chain:
Higher boiling point Viscosity increases Less volatile (how easily it changes into a gas)
Why are short chain hydrocarbons more expensive than long chain ones
They are more useful as the are more flammable
They are harder to store
Describe the process of industrial fractional distillation
Crude oil is heated outside the fractionating column and enters as a vapour
Each fraction leaves the fractionating column when it reaches the temperature at which it condenses (it’s boiling point)
Each fraction goes on to be used in different ways
There are holes in the panels separating the fractions to allow lower boiling point fractions to continue to rise
The temperature decreases as you move up the column
Give the order of condensation of each fraction and the temperature at which condenses
Bitumen 350
Fuel oil 250-350
Diesel/gas oil 220-250
Kerosene 150-240
Naphtha 75-150
Gasoline 40-75
Refinery/petroleum gas
Name the number of carbons and the use as fuels of the different fractions:
Bitumen Fuel oil Diesel/gas oil Kerosene Naphtha Gasoline Refinery/petroleum gas
Bitumen: >70 carbons, road making
Fuel oil: 20-70, oil powered central heating systems
Diesel/gas oil: 15-25, cars lorries buses
Kerosene:9-16, jet aircraft fuel
Gasoline: 4-12, petrol for motor vehicles
Refinery/petroleum gas: 1-4 carbons, bottled gas eg camping gas
As the number of carbon atoms in the molecules increases what happens to the boiling point, the volatility, the viscosity and the flammability
Boiling point: increases because more energy is needed to break the intermolecular forces
Volatility: decreases, larger molecules evaporate more slowly because of the strong intermolecular attractions
Viscosity:increases, they flow less easily due to greater intermolecular attractions
Flammability:bigger hydrocarbons burn less easily
What is crude oil
Crude oil is a mixture of hydrocarbon compounds
What is the general formula for alkanes
CnH2n+2
What is the molecular formula for methane
CH4
What is the order for the molecular formula from methane to hexane
Methane Ethane Propane Butane Pentane Hextane
What do alkanes form
A homogulous series of hydrocarbons
What do compounds in a homogulous series share
Have a similar chemical formula (chemical reactions)
Show a trend in physical properties(boiling&melting point, viscosity)
Can alkane molecules be easily separated
Yes as despite having strong covalent bonds within each molecule, the molecules are attracted by intermolecular forces with are much weaker than covalent bonds and can be easily overcome
What happens to the boiling point as the carbon chain length increases
The boiling point increases as there are stinger intermolecular forces between the molecules as there are more points of contact
What happens to the viscosity and volatility of a carbon chain as the number of carbons increases
Long chain alkanes are more viscous and less volatile as the chains are longer so it is harder for the molecules to move over eachother and flow. If they are longer they have stinger intermolecular forces and are less volatile
What are isomers
Isomers have the same molecular formula but different structural and display formula
Is the boiling point of a branched isomer higher or lower than a straight one
Lower as if they were straight they have greater areas of contact between chains leading to stronger intermolecular forces, hence more kinetic energy is needed to overcome these forces
What are the options for C5H12 other than pentane
Methyl butane: CH3CH(CH3)CH2CH3
Dimethyl propane: CH3C(CH3)2CH3
What happens when an alkane is combusted
It forms water and carbon dioxide/carbon monoxide
What does the word saturated mean in terms of organic chemistry
All the carbon atoms are joined by single bonds
