C9/10: Hydrocarbons Flashcards
(33 cards)
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
REACTION OF HYDROGEN WITH ALKENES ?
Give word equn/conditions/explain
pentene + hydrogen —> pentANE
- becuase of C=C bond , moleucles dnt contain max no. hydrogens
- addition of H2 atoms across double bond forms an ALKANE (SATURATED HYDROCRABON)
CONDITIONS: 150 degrees using NICKEL catalyst
Reaction of steam and ALKENES ?
word equn/conditions for reaction
ethene + steam —-> ETHANOL
- alcohol produced becuase O - H bond added AND C= C bond becomes single
conditions:
- 330 degrees
- 60-70 atm
- concentarted phosphoric acid catalyst
Reaction of halogens with alkenes?
word equn
ethene + chlorine —> dichloroethane
C=C turns to single bond
alcohols general formula?
CnH2n+1OH
Alcohol name and molecular formular ?
METHANOL : CH3OH
ETHANOL: C3CH2OH
PROPANOL : C3CH2CH2OH
BUTANOL : C3CH2CH2CH2OH
Fermnetation to produce alcohol?
conditions/word equn
CONDITIONS -fermented between 25 degrees +
- no oxygen
Glucose + enzymes —-> ethanol + Co2
combustion of alcohol
word equn
ethanol + oxygen —> carbon dioxide + water
reaction of alcohol with oxidising agent?
word equn
ethanol + oxidising agent —> ethanoic acid + water
FORMS CARBOXYLIC ACID+ WATER
Reaction of alcohol with sodium?
sodium + methanol —> sodium methoxide + hydrogen
- PRODUCE HYDROGEN GAS/METAL SALT
