2.4 Esters, Fats and Oils

Question 1

How are esters made

Answer 1

Condensation reaction between and alcohol and a carboxylic acid

Question 2

What is a condensations reaction

Answer 2

Two or more small molecules joining to form a larger molecule with the elimination of a smaller molecule e.g. water

Question 3

What is hydrolysis

Answer 3

Breaking down of larger molecules into smaller molecules by reaction with water

Question 4

What is always formed when an ester is made

Answer 4

Water

Question 5

How is the water formed when making an ester

Answer 5

The alcohol loses a -H and the acid loses an -OH

Question 6

How do you name an ester

Answer 6

The alcohol first the acid second e.g. Ethanol + Propanoic acid > ethyl propanoate + water

Question 7

Give three uses for esters

Answer 7

Flavourings in food, Perfumes and Solvents

Question 8

Is an ester polar or non-polar

Answer 8

non-polar

Question 9

What alkali is used for the hydrolysis of an ester

Answer 9

Sodium hydroxide

Question 10

What method of hydrolysis is used to hydrolyse an ester

Answer 10

Heating under reflux

Question 11

What are the steps for hydrolysis of an ester

Answer 11

1. Condenser 2. Distillation (the salt and the alcohol formed can be separated because they have different boiling points)

Question 12

What are the products if hydrolysis using an alkali

Answer 12

An alcohol and the salt of the carboxylic acid

Question 13

What are fats and oils an example of

Answer 13

Esters

Question 14

What is the alcohol present in fats and oils

Answer 14

Propan-1,2,3-triol (Glycerol)

Question 15

Why can glycerol be called a trihydric acid

Answer 15

Because it has 3 -OH groups

Question 16

What is the make up of a fat or oil

Answer 16

! mole Glycerol and 3 moles of long chain fatty acids

Question 17

What is the catalyst used during hydrolysis of a fat or oil

Answer 17

Sulphuric acid

Question 18

What is the products of hydrolysis of a fat or oil

Answer 18

1 glycerol molecule and 3 fatty acids

Question 19

Are oils saturated or unsaturated

Answer 19

Unsaturated

Question 20

Why are oils unsaturated

Answer 20

Due to the presence of at least 1 carbon to carbon double bond

Question 21

What state are oils in at room temperature

Answer 21

Liquid

Question 22

Why do oils have lower melting and boiling points

Answer 22

C=C bonds are not flexible and so molecules cannot pack closely together, this means van der Waals are weak oil is liquid at room temp

Question 23

Why are fats saturated

Answer 23

They only contain carbon to carbon single bonds

Question 24

Why do fats have higher melting and boiling points

Answer 24

C-C are flexible and pack closely together so have larger van der Waal forces and at solid at room temp

Question 25

What is the catalyst used in the hydrogenation of oils

Answer 25

Nickel

Question 26

What happens during hydrogenation of an oil

Answer 26

Addition of hydrogen ‘Hardens’ the oil and turns it into a saturated fat meaning the molecules can pack more closely together

Question 27

Which of oils and fats are considered to be healthier

Answer 27

Oils