Presentation on theme: "Alkanes From Crude Oil (a mixture of Hydrocarbons) Cracking"— Presentation transcript:
1Alkanes From Crude Oil (a mixture of Hydrocarbons) Cracking Pass Alkane overHEATED Al2O3 catalystFractional DistillationAlkanesUsesNon Renewable sourceReactivityNo Reaction with acid or alkalisNo Reaction with Br2?
2Fractional Distillation Separation by Boiling PointEach fraction has a different number of Carbons (C1-C4) (C5-C7) (C8-C10)…(C30-C40)What varies as the molecule size changes?Home
3UsesFuelsWhat do we do when we use them as fuels?Feedstock for alkenes
4Practical One Place a small amount of Hexane (C6H14) Octane (C8H18) Paraffin (C20H42)Onto a heat proof mat in turn and ignite with a Bunsen BurnerHow easy to they ignite?How sooty is the flame?What products are formed in a good supply of Oxygen?What products are formed in a poor supply of Oxygen?Why do the flames get more sooty?
5CombustionEase of combustion decreases as more C in alkane Flame gets more sooty as more C in alkane CO2 and H2O formed ONLY if oxygen supply is good CO and C (soot) formed if poor air supply (Called INCOMPLETE combustion) As alkanes have more C in molecule more moles of O2 per mole of alkane are required for complete combustion WRITE EQUATIONS
6Ease of combustion Vapour Burns Less Vapour as molecule increases in size at same temperatureStronger VDWHOME
7Isomerisation and Reforming Weakens VDW so more vapour Better ignition Straight to BranchedStraight to cyclic
8Practical 2 Reactions of alkanes Observations of Bromine reaction Br2 decolourised AND an acidic gas producedReaction only occurs when UV light is present
14CrackingIs the product a bigger or smaller molecule than the paraffin?Is the product more or less flammable than the paraffin?What happens when Br2 is added to the product?Smaller as it is a gas (so weaker VDW so lower bp)More flammable (as it is a gas already)Br2 decolourised without UV light (it is an alkene)HOME