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Organic chemistry
IGCSE chemistry, organic chemistry
Question | Answer | Extra |
---|---|---|
General formula for alkynes | CnH2n-2 | |
General formula for alkenes | CnH2n | |
General formula for alkanes | CnH2n+2 | |
CaC2 + 2H2O -> | ->Ca(OH)2 + C2H2 (ethyne/acetylene) | |
Preparing ethyne | Water added to calcium carbide. | Ethyne burns with a very sooty flame unless in excess oxygen, eg 'oxy acetylene' torches |
Preparing ethene in lab | Dehydrate ethanol with concentrated H2SO4 (gives poor yield) | Ethene is an important industrial gas |
Preparing ethene by cracking | Cracking saturated hydrocarbons via steam cracking naptha compounds (C4-C12) | |
Properties alkenes /alkynes | Non polar, insoluble in water, low M.p/B.p but increase with size | |
Sustitution | Alkanes with halogens, halogen atoms swap with hydrogen, hydrogen halide gas as a product, requires UV light | |
C2H6 + Br2 -(UV)> | ->C2H5Br + HBr | |
Complete combustion of alkanes | CO2+H2O produced | Only in excess of Oxygen |
Incomplete combustion | Produce CO and/ or C (soot) instead of CO2 | Limited oxygen |
Properties of alkanes | Single covalent bonds, Undergo combustion and substituion reactions, nonpolar(insoluble in water) Low MP/BP (increases with size), Less dense than water(float) | Found in natural gas (esp methane, ethan and propane) and crude oil |
Isomer | Different form of same molecular formula with a different structural formula | (blank) |
Meth- | 1 carbon | (blank) |
Eth- | 2 carbons | (blank) |
Prop- | 3 carbons | (blank) |
But- | 4 carbons | (blank) |
CH2=CH2 + H2O -(dil. H2SO4/H3PO4)-> | ->CH3-CH2-OH | Hydration |
Functional group | The specific arrangement of atoms and/or bonds responsible for the main physical +chemical properties | (blank) |
Homologous series | Family of hydrocarbons with same functional group. Similar chemical + physical properties | The main homologoud series' alkanes, alkenes and alkynes |
Hydration | Adding water to alkene, forms alcohols | Catalyst = dilute H2SO4 or H3PO4 |
Halogenation | Adding a halogen to alkene, forms halogenoalkanes | (blank) |
Testing for unsaturation | Bromine water, decolourises from orange/brown to colourless | (blank) |
Hydrogenation | Adding hydrogen to an alkene, forms an alkane | Catalyst = nickel or platinum use at 150degrees |
CH2=CH2 + H2 -(nickel/platinum)-> | ->CH3-CH3 | Hydrogenation |
CH2=CH2 + Br2 -> | CH2BrCH2Br | Halogenation |