C3.6 Alcohols, Carboxylic Acids and Esters

Question 1

What is the functional group of alcohols?

Answer 1

• OH

Question 2

What is the functional group of carboxylic acids?

Answer 2

• COOH

Question 3

What is the functional group of esters?

Answer 3

• COO

Question 4

What is a homologous series?

Answer 4

A group of chemicals that react in a similar way because they have the same functional group.

Question 5

Name two uses of alcohols.

Answer 5

• Solvents (e.g to clean paint brushes, as a solvent for perfumes and aftershave lotions) - Fuel

Question 6

What are the first three alcohols in their homologous series and their formulas?

Answer 6

• Methanol - CH₃OH - Ethanol - C₂H₅OH - Propanol C₃H₇OH

Question 7

Describe the properties of methanol, ethanol and propanol.

Answer 7

• They are flammable - They burn in air to produce carbon dioxide and water - They dissolve completely in water to form colourless solutions - They react with sodium to give hydrogen and alkoxides

Question 8

Name one use of ethanol (it’s quite obvious) and the effect it has.

Answer 8

It is used as the main alcohol in alcoholic drinks - it can damage the liver and brain.

Question 9

Why are alcohols used as solvents?

Answer 9

They can dissolve most of the compounds water can but many that water can’t e.g hydrocarbons, oils and fats

Question 10

Name the first three carboxylic acids in their homologous series and their formulas.

Answer 10

• Methanoic acid : HCOOH - Ethanoic acid : CH₃COOH - Propanoic acid : C₂H₅COOH

Question 11

How is ethanoic acid made?

Answer 11

• By oxidising ethanols, this is either done by fermenting ethanol using yeast/bacteria or with oxidising agents. - ethanol + oxygen ====> ethanoic acid + water

Question 12

What the strength of an acid?

Answer 12

How well it ionises in water

Question 13

How do carboxylic acids dissolve in water (and why does it make them weak acids)?

Answer 13

• They dissolve in water to produce acidic solutions, by ionising and releasing H+ ions which are responsible for making the solution acidic. - However, they don’t ionise completely (release enough H+ ions) so they just form weak acidic solutions.

Question 14

What is the solutions of carboxylic acids like compared to solutions of strong acids with the same concentration?

Answer 14

They have a higher pH (less acidic)

Question 15

How do carboxylic acids react with carbonates?

Answer 15

They produce carbon dioxide and compounds ending in -anoate e.g ethanoic acid + sodium carbonate ===> carbon dioxide + sodium ethanoate

Question 16

What is ethanoic acid mainly used for?

Answer 16

It is dissolved in water to make vinegar, which is used for flavouring and preserving foods

Question 17

What are two uses of carboxylic acids?

Answer 17

• Soaps - To make esters

Question 18

How are esters made?

Answer 18

By reacting alcohols and carboxylic acids under an acid catalyst (e.g sulfuric acid)

Question 19

Name and explain two uses of esters

Answer 19

• Perfumes and flavourings - They smell and taste nice - They are volatile (evaporate easily) which is ideal for perfumes

Question 20

What are the properties of esters?

Answer 20

• They are very flammable - Volatile - They don’t mix well with water, not as soluble as alcohols and carboxylic acids - They do mix well with alcohols and organic solvents

Question 21

What are the dangers of esters?

Answer 21

• They are highly flammable - Ester fumes are heavier than air, so inhaling them irritates mucous membranes in the mouth - Toxic in large doses

Question 22

Give the equation for the reaction between ethanol and ethanoic acid to make an ester.

Answer 22

ethanol + ethanoic acid ===> ethyl ethanoate

Question 23

What do ester compound names look like?

Answer 23

—-yl —-anoate

Question 24

Draw the structure of ethanoic acid.

Answer 24

Question 25

Draw the strucuture of ethanol

Answer 25