B15 Alcohols, alkanoic acids and esters

Question 1

What is the functional group for an alcohol?

Answer 1

hydroxyl group, -OH

Question 2

True or False: alcohols are named by using the prefix which indicates the total number of carbon atoms in the molecule plus the ending ‘-anol’.

Answer 2

true

Question 3

Name the alcohol that has five carbon atoms.

Answer 3

pentanol

Question 4

What is the general formula of an alcohol?

Answer 4

CnH2n+1OH

Question 5

True or false: alcohol molecules are not polar

Answer 5

false. Alcohol molecules are polar due to the presence of the polar -OH group.

Question 6

Alcohols are less volatile than their corresponding alkanes because ___________.

Answer 6

Because of the polar nature of the molecules. It causes the forces of attraction between the alcohol molecules to be stronger than between the non-polar alkane molecules.

Question 7

Which of the following statements is true?
A. Polar solvents dissolve in polar solutes.
B. Non-polar solutes dissolve in polar solvents.
C. Polar solutes dissolve in polar solvents.

Answer 7

C. Polar solutes dissolve in polar solvents.

Question 8

What products are formed during combustion of ethanol?

Answer 8

carbon dioxide and water

Question 9

Write a chemical equation which summarises the complete combustion of ethanol.

Answer 9

C2H5OH (l) + 3O2 (g) ——> 2CO2 (g) + 3H2O (g)

Question 10

True or False: Ethanol burns with a clear blue flame

Answer 10

True, because the ratio of carbon to hydrogen atoms in the molecule is low. All the carbon is converted to carbon dioxide- none remains to produce soot.

Question 11

Complete the chemical equation:

2C2H5OH (l) + 2Na (s) —–> ?

Answer 11

2C2H5OH (l) + 2Na (s) —–> 2C2H5ONa (alc sol) + H2 (g)

Question 12

What conditions are necessary for the dehydration of ethanol?
A. Heat and concentrated H2SO4
B. 5 atm pressure and 200 degrees Celcius
C. Heat
D. Concentrated H2SO4 and 170 degrees Celcius

Answer 12

D. Concentrated H2SO4 and 170 degrees Celcius

Question 13

What product is formed when the elements of water are removed from an alcohol?

Answer 13

The corresponding alkene e.g. ethanol - water —-> ethene

Question 14

During the breathalyser test to detect the presence of ethanol on a driver’s breath, the ethanol:
A. oxidises the green Cr3+ ion to the orange Cr2O7 ion
B. reduces the orange Cr2O7 ion to the green Cr3+ ion
C. reduces the green Cr3+ ion to the orange Cr2O7 ion
D. oxidises the orange Cr2O7 ion to the green Cr3+ ion

Answer 14

B. reduces the orange Cr2O7 ion to the green Cr3+ ion

Question 15

True or False: Ethanol is oxidised to ethane when heated with acidified potassium manganate (VII) or acidified potassium dichromate (VI).

Answer 15

False: Ethanol is oxidised to ethanoic acid when heated with acidified potassium manganate (VII) or acidified potassium dichromate (VI).

Question 16

Describe fermentation.

Answer 16

It is the chemical reaction in which carbohydrates are converted into ethanol by yeast under anaerobic conditions. Wine and rum are made by fermentation.

Question 17

What is the general formula for alkanoic acids?

Answer 17

CnH2n+1COOH

Question 18

The functional group of alkanoic acids is the _____ group, _____.

Answer 18

The functional group of alkanoic acids is the carboxyl group, - COOH.

Question 19

True or False: Alkanoic acid molecules are polar.

Answer 19

True

Question 20

Alkanoic acids are less volatile than their corresponding alkanes, because _____.

Answer 20

Because the forces of attraction between the polar alkanoic acid molecules are stronger than between the non-polar alkane molecules.

Question 21

metals + alkanoic acid —–> ?

Answer 21

metals + alkanoic acid —-> salt + hydrogen

Question 22

metal oxide + alkanoic acid —–> ?

Answer 22

metal oxide + alkanoic acid —–> salt + water

Question 23

alkali + alkanoic acid —–> ?

Answer 23

alkali + alkanoic acid —-> salt + water

Question 24

carbonates + alkanoic acid ——> ?

Answer 24

carbonates + alkanoic acid —-> salt + water+ carbon dioxide

Question 25

sodium bicarbonate + alkanoic acid ----> ?

Answer 25

sodium bicarbonate + alkanoic acid ----> salt + water + carbon dioxide

Question 26

Define esterification.

Answer 26

This is the process in which a carboxylic acid reacts with an alcohol to produce an ester and water.

Question 27

What are the conditions necessary for esterification?

Answer 27

concentrated H2SO4 (catalyst, dehydrating agent) and heat

Question 28

What is the general formula for esters?

Answer 28

CnH2n+1COOCxH2x+1

Question 29

The functional group for esters is _______.

Answer 29

-COO-

Question 30

True or False: Sugars and salts are esters.

Answer 30

False. Fats and oils are esters.

Question 31

Summarise esterification using a word equation.

Answer 31

alkanoic acid + alcohol --conc. H2SO4 and heat----> ester + water

Question 32

butanol + propanoic acid ---> ?

Answer 32

butanol + propanoic acid ----> butyl propanoate + water

Question 33

Briefly describe acid hydrolysis of esters.

Answer 33

The ester is heated with an acid catalyst such as dilute hydrochloric or sulfuric acid.

Question 34

Does this equation accurately summarise acid hydrolysis of ethyl ethanoate? CH3COOC2H5 (l) + H20 (l) --conc. H2SO4, heat----> CH3COOH (l) + C2H5OH (l)

Answer 34

Yes.

Question 35

True or False: During alkaline hydrolysis, the ester is heated with sodium and potassium carbonate.

Answer 35

False. During alkaline hydrolysis, the ester is heated with sodium and potassium hydroxide solution.

Question 36

Which of the following are true for saponification? I. it is the alkaline hydrolysis of large esters II. it produces water and a salt III. it is used in the manufacture of soap A. I only B. I and III only C. II only D. I, II and III

Answer 36

B. I and III only

Question 37

The ionic head is the ________ end of a detergent molecule and the tail is the ____________ end.

Answer 37

The ionic head is the hydrophilic end of a detergent molecule and the tail is the hydrophobic end.

Question 38

State two ways in which a soap prepared from a fat or oil differs from a soapless detergent.

Answer 38

Soapy detergents do not lather easily in hard water, while soapless detergents lather in hard water. Soapy detergents are biodegradable, while soapless detergents are non-biodegradable.