chemistry lab on saturated and unsaturated fats

Topics: Fat, Chemistry, Titration Pages: 4 (498 words) Published: October 22, 2013
20

9.

Classic chemistry experiments

Unsaturation
in fats and oils

Topic
Organic chemistry, saturated and unsaturated fats.

Timing
45 min.

Description
The students titrate different oils and fats mixed with Volasil against bromine water.

Apparatus and equipment (per group)
w White tile
w Conical flask
w Dropper pipette. (Use the type of teat pipette usually fitted to Universal Indicator bottles, that do not allow squirting – eg Griffin.)
w Burette (filled with bromine water)
w Boss
w Clamp
w Stand.

Chemicals (per group)
–3

w Bromine water (Harmful and irritant) 0.02 mol dm (This concentration does not have to be accurate, but if the concentration is reduced, less fat will be required to ensure sensible volumes of bromine water are used.)

w Volasil (Volasil 244 from BDH) (This is a mixture of organic chemicals which can act as a solvent for this experiment.)
w Cooking oil (animal)
w Cooking oil (vegetable)
w Olive oil.

Teaching tips
Other fats can be tried – eg melted butter, melted lard, melted margarine, and specific products such as Flora and Clover.
–3

This experiment has also been trialled using KMnO4(aq) (0.0005 mol dm ) as the indicator. This turns from purple to colourless while unsaturation is still present. The procedure is the same as for bromine water, but portions of the potassium permanganate are added with swirling until the mixture fails to produce a colourless solution. The mixture requires more and more swirling as the amount of potassium permanganate increases. Warming fats in the Volasil using a beaker of hot water helps the fat dissolve and also speeds up the reaction.

This experiment should be done in a fume-cupboard with ready filled burettes.

Background theory
Saturation and unsaturation.

Classic chemistry experiments

21

Safety
Wear eye protection.

Answers
1. Depends on what is supplied.
2. Weighing the fats and oils and calculating the exact amount of bromine water used...
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