Alcohols and Carboxylic Acids (2)

Question 1

What is the

functional group of alcohols?

Answer 1

-OH

Question 2

What is the

general formula of an alcohol?

Answer 2

CnH2n+1OH

Question 3

How can you

dehydrate alcohols?

Answer 3

by heating a mixture of an alcohol and acid catalyst

this forms an alkene and water

Question 4

What is

fermentation?

and what is the word equation for this?

Answer 4

the process of using yeast to produce alcohols from carbohydrates

glucose –yeast–> ethanol + carbon dioxide

Question 5

Describe how you would make a

solution of ethanol by fermentation.

(5 steps)

Answer 5

1. Mix yeast and a solution of carbohydrate in a clean container.
2. Seal the container and leave it in a warm place. (Keep the mixture between 30-40°C.)
3. Keep the mixture in anaerobic conditions (no oxygen). This would convert the ethanol to ethanoic acid.
4. When the concentration of alcohol reaches 10-20%, the fermentation reaction stops because the yeast gets killed off by the alcohol.
5. The yeast will fall to the bottom of the container and you can collect the ethanol solution from the top.

The fermented mixture can be distilled to produce more concentrated alcohol.

Question 6

How would you make a

concentration of ethanol above 20%?

(from the fermented solution)

Answer 6

fractional distillation

the ETHANOL evaporates first

Question 7

Describe an experiment to

investigate alcohols as fuels.

(6 steps)

Answer 7

1. Put some alcohol in a spirit burner and measure the mass of the burner and fuel using a mass balance.
2. Measure 100ml distilled water into a copper calorimeter.
3. Insulate the calorimeter by using a draught excluder, then cover with an insultaing lid after placing a thermometer inside.
4. Take the initial temperature of the water then put the burner under the calorimeter and light the wick.
5. Stir the water throughout using the thermometer. When the heat from the burner has made the temperature of the water rise by 20°C, blow out the spirit burner.
6. Immediately reweigh the spirit burner and calculate the mass of fuel that has been used.
7. Repeat the experment using other alcohols.

Question 8

What are

carboxylic acids?

Answer 8

a group of compounds that all contain a -COOH functional group

these are weak acids

Question 9

How are

carboxylic acids formed?

Answer 9

by the oxidising of alcohols using an oxidising agent

Question 10

Define

homologous series.

Answer 10

a group of similar compounds that all have the same functional group and formula