IGCSE Chemistry - Hydrocarbon tests

cracking - alkanes

600-700 degrees temp.

alumina/silica

substitution - alkanes

uv light

addition - alkenes

none

alkanes general formula

cnh2n+2

alkenes general formula

cnh2n

alcohol general formula

cnh2n+1oh

alcohol 3 types - oxidation

• Combustion (burning in air)

• Aerobic oxidation

• Treatment with an oxidising agent

complete combustion of alcohol

characteristic - almost invisible blue flame

why schools use ethanol in spirit burners - burns cleanly without a strong odour

microbial oxidation of alcohol

• Bacteria in the air use oxygen to oxidise the ethanol in the wine:

ethanol + oxygen → ethanoic acid + water

wine (left open) - microbial oxidation of ethanol will produce a weak solution of the carboxylic acid, ethanoic acid, the same acid used in vinegar

oxidisation agent - alcohol

potassium dichromate(VI) solution

(orange to green)
sulfuric acid

equation:

CH₃CH₂OH + [O]  →  CH₃COOH + H₂O

hydration of ethene - ethanol

300 degrees

60-70atm

concentrated phosphoric acid (catalyst)

ethanol steps (hydration of ethene)

1. ethene produced by cracking

2. hydrated

3. condensed (ethanol has lower b.p than ethene)

4. fractional distillation (separate ethanol from water)

fermentation - ethanol

glucose

30degrees

enzymes in yeast

absence of oxygen

C₆H₁₂O₆ → 2CO₂ + 2C₂H₅OH

carboxylic acid general formula

cnh2n+1cooh

esters functional group

o—c-o

esters features

sweet smelling

catalyst of esterification

concentrated sulfuric acid