Carboxylic acids, esters & fats/oils

Question 1

How can carboxylic acids be identified?

Answer 1

the presence of the carboxyl group (-COOH) and the -oic ending.

Question 2

What can carboxylic acids react with bases e.g. alkalis to form (neutralisation)?

Answer 2

salts e.g. sodium ethanoate

Question 3

What can carboxylic acids be reduced to ?

Answer 3

aldehydes and alcohols

Question 4

What does a reduction reaction involve?

Answer 4

a gain of hydrogen or loss of oxygen which results in a decrease in the oxygen to hydrogen ratio

Question 5

What are esters made by?

Answer 5

a condensation reaction

Question 6

What is a condensation reaction?

Answer 6

where 2 small molecules join together to make a larger and water

Question 7

What is the reaction which produces esters?

Answer 7

esterification

Question 8

What is the equation for the formation of an ester?

Answer 8

alcohol+ carboxylic acid > ester + water

Question 9

What do all esters contain?

Answer 9

the ester link

Question 10

What is the reverse reaction of condensation?

Answer 10

hydrolysis

Question 11

What are esters (naming)?

Answer 11

alkyl alkanoates

Question 12

What are the properties of esters?

Answer 12

Esters are immiscible with water (because water is polar whereas esters are non-polar).
Esters are sweet-smelling and volatile (low boiling point)

Question 13

What are the uses of esters?

Answer 13

flavourings for food
perfumes
solvents for non-polar substances

Question 14

Describe the experimental set up for making esters?

Answer 14

Hot water bath (used as contents are flammable)
test tube containing alcohol and acid + conc sulphuric acid as a catalyst.
wet paper towel as a condenser (reflux (reflow) cuts down evaporation)
cotton wool
sodium hydrogen carbonate solution (neutralises acids & stops the reaction. Separates ester (oily layer)

Question 15

What does the equilibrium mixture contain?

Answer 15

carboxylic acid/ alcohol/ ester/ water

Question 16

What are fats and oils?

Answer 16

esters

Question 17

What is the alcohol in fats/oils?

Answer 17

glycerol

Question 18

What is the systematic name for glycerol?

Answer 18

propan-1,2,3-triol

Question 19

What does glycerol have?

Answer 19

3 hydroxyl groups

Question 20

Glycerol has 3 hydroxyl groups but what does this mean for fats/oils?

Answer 20

3 ester links

Question 21

What is the ratio to form one fat/oil?

Answer 21

1 glycerol : 3 fatty acid molecules

Question 22

What is a fatty acid?

Answer 22

very long hydrocarbon chain with a carboxyl group

Question 23

What is the reaction called when glycerol + fatty acids > lipids?

Answer 23

condensation

Question 24

What is the reaction called when fats> glycerol +fatty acids?

Answer 24

hydrolysis

Question 25

What are fats/oils also called?

Answer 25

triglycerides | lipids

Question 26

What are all fats and oils (saturated or unsaturated) classified as?

Answer 26

``` Animal Vegetable Marine (fish oils) high energy foods provide essential fatty acids contain some vitamins (dissolved in the fats/oils) ```

Question 27

What are the 2 groups fatty acids are divided into?

Answer 27

saturated fatty acids (e.g stearic acid (C17H35COOH) found in animal fats) Unsaturated fatty acids (e.g. oleic acid (C17H33COOH) found in vegetable oils)

Question 28

What do unsaturated have that allows them decolourise bromine water?

Answer 28

C=C

Question 29

What are the differences between fats and oils?

Answer 29

Fats are solids whereas oils are liquid. | Solid fats have saturated chains whereas liquid oils have unsaturated chains.

Question 30

Why do saturated fats and unsaturated oils have different melting points?

Answer 30

The saturated, regularly shaped fat molecules pack closely and have lots of London dispersion forces between them > higher m.pt. Unsaturated oil molecules have irregular shapes (caused by C=C). They pack loosely and have fewer London dispersion forces > lower m.pt.

Question 31

How can oil become fats?

Answer 31

By hydrogenation/ adding hydrogen

Question 32

When oils harden and become fats what happens?

Answer 32

they become saturated and m.pt is raised. margarine is an example of this

Question 33

When oils are hardened what are the fats formed called?

Answer 33

hydrogenated fats

Question 34

What does too much saturated fats/ animal in our diet cause?

Answer 34

heart disease