Exam (elaborations)
Chromatography Lab – Qs & As (Verified)
- Course
- CHROMATOGRAPHY
- Institution
- CHROMATOGRAPHY
Chromatography Lab – Qs & As (Verified)
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Chromatography Lab – Qs & As (Verified)What were food color additives initially used for? ✔️Ans - To make food
more visually appealing to the consumer and mask poor quality.
Why were almost all of the original food color additives phased out? ✔️Ans -
Most were not safe for consumption and were being added to foods with no
health testing.
What could have been done to determine whether a color additive was
harmful before it was used in the food industry? ✔️Ans - They could have
used chromatography to determine the purity of each additive.
Of the original 695 color additives how many are still used today? ✔️Ans - 2
How many color additives total are used today? ✔️Ans - 7
What do all approved food dyes share in common? ✔️Ans - They are
charged, water-soluble organic compounds that bind to natural ionic and
polar sites in large food molecules.
What is the difference between absorption and adsorption ✔️Ans -
Absorption is a physical and chemical event occurring during contact between
materials that have an attraction for each other. Adsorption is different from
absorption in that the molecules of the material physically adhere to the
adsorbent rather than being absorbed into the interspaces of the absorbent
material.
What is chromatography used for? ✔️Ans - To separate organic compounds
for identification or purification.
What are the two main components of chromatography? ✔️Ans - Adsorbent
& eluent
What is another name for the adsorbent? ✔️Ans - Stationary phase
(chromatography paper)
What is another name for the solvent or eluent? ✔️Ans - Mobile phase
, What concept does chromatography work on? ✔️Ans - Compounds to be
separated are slightly soluble in the eluent and will spend some of the time in
the eluent and some of the time in the adsorbent.
What factors determine whether the separation by an eluent will be
successful? ✔️Ans - The affinity of a substance for the eluent versus the
adsorbent allows molecules to be separated by chromatography. (Depends on
polarity)
How can you judge whether a mixture was separated properly by
chromatography? ✔️Ans - If you can clearly see all of the separate colors of
a mixture and they have practically stopped moving as the eluent continues to
make its way up the paper.
Why does changing the polarity of the eluent affect the separation of a mixture
so much? ✔️Ans - Changing the polarity of the eluent will only slightly affect
the solubility of the molecules but may greatly change the relative attraction
for the adsorbent.
What is capillary action? ✔️Ans - The ability of a liquid to flow against
gravity up a narrow tube or porous material.
Where do you put the eluent and carry out the separation? ✔️Ans -
Erlenmeyer flask
What is the most difficult task in chromatography? ✔️Ans - Choosing the
eluent is the most difficult task because the polarity determines the level of
separation that will be achieved; different samples will spend varying amount
of time interacting with the paper and solvent.
What is the rate of flow and what else is it called? ✔️Ans - The rate of flow is
the distance a sample moves along a paper in comparison to the overall
distance the solvent travels; also called the Rf value.
How is the rate of flow calculated? ✔️Ans - Distance sample travels/ overall
distance solvent travels
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