chemistry - separate chemistry 2: alcohols & carboxylic acids (9.26 - 9.34)

9.26 methanol formula

CH₃OH

9.26 methanol structure

9.26 ethanol formula

C₂H₅OH

9.26 ethanol structure

9.26 propanol (propan-1-ol) formula

C₃H₇OH

9.26 propanol (propan-1-ol) structure

9.26 butanol (butan-1-ol) formula

C₄H₉OH

9.26 butanol (butan-1-ol) structure

9.27 alcohols functional group

-OH

9.27 what happens when alcohols are dehydrated?

alcohols dehydrated to form alkenes

9.28 core practical: investigate temp. rise produced in known mass of water by combustion of alcohols ethanol, propanol, butanol & pentanol

1. measure mass of alcohol burner & cap

2. record mass & name of alcohol

3. place alcohol burner in centre of heat-resistant mat

4. use measuring cylinder to add 100cm³ cold water to conical flask

5. measure & record initial temp. of water

6. clamp flask above alcohol burner

7. light wick of burner & allow water to heat up by about 40°C

8. replace cap on burner & measure & record final temp. of water

9. measure mass of alcohol burner & cap again & record mass

10. calculate mass of alcohol burned to produce 1°C rise in temp.

11. repeat steps 1-10 using fresh, cold water & diff. alcohol

9.29 methanoic acid formula

HCOOH

9.29 methanoic acid structure

9.29 ethanoic acid formula

CH₃COOH

9.29 ethanoic acid structure

9.29 propanoic acid formula

C₂H₅COOH

9.29 propanoic acid structure

9.29 butanoic acid formula

C₃H₇COOH

9.29 butanoic acid structure

9.30 carboxylic acids functional group

-COOH

9.30 what properties do solutions of carboxylic acids have?

solutions of carboxylic acids have typical acidic properties

9.31 what happens when ethanol is oxidised?

ethanol oxidised to produce ethanoic acid (+ water)

9.31 what happens when alcohols are oxidised?

produce carboxylic acids (+ water)

9.32 what do members of given homologous series have in common?

similar reactions

9.32 what do members of given homologous series have similar reactions?

molecules contain same functional group

what do alcohols produce when completely combusted?

carbon dioxide + water

9.33 production of ethanol

carbohydrate starch broken down into sugars

plant material containing sugars mixed with water & yeast

enzymes in yeast turn sugars → ethanol & CO₂ in fermentation

glucose → ethanol + carbon dioxide

what type of respiration is yeast fermentation?

anaerobic respiration

9.34 how to obtain concentrated solution of ethanol?

fermentation only produces alcohol concs. up to 15% - higher concs. kill yeast cells

more concentrated solutions of ethanol formed by fractional distillation

b.p of ethanol < b.p. of water

1. heated liquids evaporate

2. vapours cool as rise up fractionating column

3. ethanol has lower b.p. - remains gas for longer, separates from water

4. first fraction/distillate collected contains higher % of ethanol