C9/10: Hydrocarbons Flashcards
alkanes general formula?
CnH2n+2
names of alkanes and molecular formula?
METHANE - CH4
ETHANE - C2H6
PROPANE - C3H8
BUTANE - C4H10
hydrocarbons?
compound that only conatisn hydrogen and carbon atoms.
franction distillation of crude oil?
- crude oil enters bttom of colum as HOT VAPOUR
- Vapour rises/vapours with high BP condense lower down in column
- vapours with lower BP condense high up column
- different fraction condense at different levels according to BP (get colder up the column)
5.fractions containing BIGGER HYDROCARBONS collected at bottom/SMALER collected at top
properties of alkanes?
BP increases as molcule gets bigger (intermolecular forces are larger due to more electrons/greater SA contact with them, so more energy is needed to break them)
VISCOCITY - as molecules get bigger, so do IF
- MORE VISCOUS , BETTER LUBRICANTS
FLAMMABILITY - INCREASED SIZE, LESS FLAMMABLE
combustion of alkanes eg
methane + oxygen —> carbon dioxide + water
ALKANES?
saturated hydrocarbons containing single bonds only
ALKENES?
unsaturated hydrocarbons containing double bonds
what is cracking?
- converts long chain of alkane molecules into samller chain molecules that are more useful
- ALKENES/HYDROGEN are produced using this process
process of CATALYTIC CRACKING?
- heat hydrocarbon to 470-550 to vaporise them
- vapours pass over hot powdered ctatalyst of ALUMINIUM OXIDE
- this breaks covalent bonds, causing THERMAL DECOMPOSITION
- molecules are broken up RANDOMLY to produces smaller alkanes/alkenes
process of steam cracking?
- vaporised hydrocarbons are mixed with steam/heated at high temps which induces cracking
alkenes general formula?
CnH2n
what happens when alkenes are added to bromine water?
- addition reaction
- ALKENES turn bromine water COLOURLESS, because the double bond breaks and each bromine is bonded with each carbon , so no Bromine atoms are free, so loses its colour
Names of alkenes and molecular formula?
ETHENE : C2H4
PROPENE: C3H6
BUTENE: C4H8
PENTENE : C5H10
INCOMPLETE COMBUSTION OF ALKENES?
word equn
Butene + Oxygen —> Carbon MONOXIDE + water