3.3.9 Carboxylic Acids and Derivatives

Question 1

What type of acid are carboxylic acids?

Answer 1

Weak

Question 2

How do carboxylic acids react with carbonates? (2)

Answer 2

Forms carboxylate salt + water + carbon dioxide

Fizzing indicates CO2

Question 3

What is esterification? (2)

Answer 3

The reversible reaction between carboxylic acids and alcohols to form esters and water
Conc. sulphuric acid catalyst and reflux

Question 4

What are esters used for? (4)

Answer 4

Perfume
Food flavouring
Solvent (glue, printing ink)
Plasticisers

Question 5

Acid hydrolysis of esters

Answer 5

Ester + water > carboxylic acid + alcohol

Question 6

Base hydrolysis of esters

Answer 6

Ester + OH- > carboxylate ion + alcohol

Question 7

What are vegetable oils and animal fats?

Answer 7

Esters of glycerol (propane-1,2,3-triol)

Question 8

What is a saturated fat?

Answer 8

Contains no double bonds

Question 9

What is an unsaturated fat?

Answer 9

Contains C=C double bonds

Question 10

What is the structure of a fat/oil like? (3)

Answer 10

The alcohol groups in glycerol lose the hydrogen, forming an ester bond with long chain fatty acids
Fats fit neatly together due to the saturated hydrocarbon chain, increasing the Van der Waals force’s so they are solid at room temperature
Oils pack less well as the chains are bent due to double bonds, decreasing the Van der Waals forces so they are liquid at room temperature

Question 11

Base hydrolysis of fats and oils

Answer 11

Fat/oil + 3NaOH > glycerol + 3 sodium salts (soap)

Question 12

What is soap?

Answer 12

Salts of long-chain carboxylic acids

Question 13

How can fatty acids be formed from soap?

Answer 13

React soap with an acid, displacing the Na+ ions

Question 14

How is biodiesel formed? (2)

Answer 14

Fat/oil + 3CH3OH > glycerol + 3 methyl esters

Strong alkali catalyst (KOH)

Question 15

What is biodiesel?

Answer 15

A mixture of methyl esters of long-chain fatty acids