burner 2 - soap

Question 1

name the ester used

To prepare a sample of soap by base hydrolysis/ saponification

Answer 1

Glyceryl tristearate

Question 2

name the base used

To prepare a sample of soap by base hydrolysis/ saponification

Answer 2

sodium hydroxide

Question 3

name the soap produced

To prepare a sample of soap by base hydrolysis/ saponification

Answer 3

sodium stearate

Question 4

name the alcohol produced

To prepare a sample of soap by base hydrolysis/ saponification

Answer 4

glycerol

Question 5

describe refluxing - forming the soap

To prepare a sample of soap by base hydrolysis/ saponification

Answer 5

lard/ plant oil placed into reaction flask, add sodium hydroxide IN EXCESS, ethanol and anti-bumping chips
the reactants are heated in the reaction flask and refluxed using a liebig condenser for 30 mins

Question 6

describe distillation - removing the ethanol solvent

To prepare a sample of soap by base hydrolysis/ saponification

Answer 6

The apparatus is rearranged to a distillation and the flask is heated to 78C to allow most of the ethanol to be distilled off

Question 7

describe the addition to brine- percipitating the soap

To prepare a sample of soap by base hydrolysis/ saponification

Answer 7

the reaction flask contains soap (not soluble in brine)
Glycerol
Sodium hydroxide (left over)
Ethaol (un-distillated)
the reaction misture is poured from the hot reaction flask into a beaker of brine solution, rinising the reaction flask with the MINIMUM amount of boiling water to remove any residue remaning and adding it into the brine

Question 8

describe the filtration, washing and drying of soap

To prepare a sample of soap by base hydrolysis/ saponification

Answer 8

the soap is filtered using vaccuk/ suction filtration.
the soap is washed with fresh brine followed by ice water The soap is left to air dry on the filter paper in a dry and warm place

Question 9

why is oil or lard used in this expeirment

To prepare a sample of soap by base hydrolysis/ saponification

Answer 9

they contain naturallly occouring esters- hydrolysis and ester with a base will produce a soap

Question 10

why is sodium hydroxide added to the reaction flask

To prepare a sample of soap by base hydrolysis/ saponification

Answer 10

sodium hydroxide is a base used

Question 11

what is the difference between soap made with sodium hydroxide and soap made with potassium hydroxide

To prepare a sample of soap by base hydrolysis/ saponification

Answer 11

soaps made with potassium hydroxide are milder than soaps made with sodium hydroxide

Question 12

why is excess bade used

To prepare a sample of soap by base hydrolysis/ saponification

Answer 12

to ensure all of the ester reacts and is converted to soap. eg the ester is the limiting reagent

Question 13

why is ethanol added to the reaction flask

To prepare a sample of soap by base hydrolysis/ saponification

Answer 13

ethanol acts as a solvent

Question 14

Why are anti-bumbing chips added to the reaction flask

To prepare a sample of soap by base hydrolysis/ saponification

Answer 14

allow boiling to take place more smoothly

Question 15

describe how the ester and base are reacted in this expeirment

To prepare a sample of soap by base hydrolysis/ saponification

Answer 15

heated under reflux until they are vapourised then are cooled back down into a liquid in the liebig condenser and fal back into the reaction flask so they can completely react

Question 16

why is the mixture refluxed? NB

To prepare a sample of soap by base hydrolysis/ saponification

Answer 16

1. allow the reactants time to react to completion
   2.Ensures no loss of the ethanol solvent

Question 17

what type of reaction occours during the reflux process

Answer 17

base hydrolysis

Question 18

as the reaction occours, what is the coating observed on the walls of the reaction flask

To prepare a sample of soap by base hydrolysis/ saponification

Answer 18

soap that has been formed
lard/ oil that has not been hydrolysed

Question 19

why is the reaction flask swirled from time to time?

To prepare a sample of soap by base hydrolysis/ saponification

Answer 19

washes the coating from the walls of the flask back into the reaction mixture

Question 20

Give a co-product of the reflux action and give a use of this product

To prepare a sample of soap by base hydrolysis/ saponification

Answer 20

glycerol-
manfacturing explosive nitro-glycerine

Question 21

give the IUPAC name for glycerol

To prepare a sample of soap by base hydrolysis/ saponification

Answer 21

propane-1,2,3triol

Question 22

Why is a distillation carried out after the refluxing stage

To prepare a sample of soap by base hydrolysis/ saponification

Answer 22

to distil off and remove the ethanol solvent

Question 23

why must the ethanol then distilled off after reflux

To prepare a sample of soap by base hydrolysis/ saponification

Answer 23

makes it easier to percipitate the soap and maximises its yeild

Question 24

what is a suitable heating method for first refluxing the reaction misture and then distilling off the ethanol

To prepare a sample of soap by base hydrolysis/ saponification

Answer 24

hot plate and a water bath - allows for gentel heating where the temperture can be easily controled

Question 25

What is brine | To prepare a sample of soap by base hydrolysis/ saponification

Answer 25

Brine is a saturated solution of sodium chloride in water

Question 26

Why is the reaction mixture added to a saturated brine solution | To prepare a sample of soap by base hydrolysis/ saponification

Answer 26

The soap does not dissolve in brine and is precipitated out of solution

Question 27

Why is a minium amount of hot water used when rinsing out the flask to remove resdue and add it to the brine | To prepare a sample of soap by base hydrolysis/ saponification

Answer 27

maxmises the amount of soap that will be perciptated

Question 28

why is the reaction mixture then filtered | To prepare a sample of soap by base hydrolysis/ saponification

Answer 28

Isolate the insoluble soap

Question 29

why is the vacuum filtration performed in prefernce to gravity filtration | To prepare a sample of soap by base hydrolysis/ saponification

Answer 29

to speed up the filtration process help dry the soap

Question 30

What two substances is the soap washed with after the filtration any why? **NB** | To prepare a sample of soap by base hydrolysis/ saponification

Answer 30

* Fresh brine- dissolved and removes any sodium hydroxide * Ice cold water- to wash of brine - ice cold to avoid any soap dissolving

Question 31

How is the soap left to dry overnight | To prepare a sample of soap by base hydrolysis/ saponification

Answer 31

the soap is placed on filter paper and left to air dry in a warm place

Question 32

What is the location of the glycerol and sodium hydroxide at the end once the soap has been collected | To prepare a sample of soap by base hydrolysis/ saponification

Answer 32

dissolved in the brine in the filtrate

Question 33

Outline a test that is performed on the prepared soap | To prepare a sample of soap by base hydrolysis/ saponification

Answer 33

the soap is added to a test tube of de- ionised water (soft water) and shaken - **the presence of a lather** *will not form a lather when added to a hard water sample*

Question 34

Give two procedures that were performed to ensure the yeild of soap obtained is maximised | To prepare a sample of soap by base hydrolysis/ saponification

Answer 34

distilling off the ethanol after the reflux stage rinsing out the reaction flask with the minium amount of boiling water and adding to the brine

Question 35

outline two safty precautions taken in this expeirment | To prepare a sample of soap by base hydrolysis/ saponification

Answer 35

wear goggles and gloves - sodium hydroxide caused take care when dealing with hot flasks and keep them in water beth to prevent overheating

Question 36

Explain why one end of a soap molecule can be describe as water loving hydrophillic and one end is described as hydrophobic | To prepare a sample of soap by base hydrolysis/ saponification

Answer 36

soap consists of a non-polar hydrocarbon portion that dissolves non-polar substances soap also consists of an ionic portion portion that dissolves salts from sweats and causes soap to dissolve in water

Question 37

what is the principal chamical difference between animal and vegtable fats | To prepare a sample of soap by base hydrolysis/ saponification

Answer 37

vegtable fats are unsaturated animal fats are saturated