Experiment 5: Extraction of Chlorophyll & Carotenes from Spinach via TLC, Column Chromatography & Micro-Extractions

Question 1

! Compounds isolated after an extraction may be impure or wet. What effect will this have on the melting points?

Answer 1

The melting points will be broader and lower than expected.

Question 2

Like the experiment last week, today you will perform a liquid-liquid extraction. The organic solvent you will use is hexane (“hexanes” to be specific…). When you mix the hexane with water, you will expect to see (how many layers and which?)?

Answer 2

two layers; the top will be hexane as hexane is less dense than water

Question 3

Think of your experiment from last week and choose which of the following is true about extracting an organic compound into a given solvent.

Answer 3

Organic substances with acidic functional groups may dissolve in water if treated with base.

Question 4

You will use 2 different kinds (thin layer & column) of chromatography as a means of separation. Both of the chromatographic experiments that you will perform will separate the components of a mixture based on which physical property?

Answer 4

polarity/solubility

Question 5

What is the Rf value for a spot that travelled 2.0 cm up a TLC plate if the solvent front travelled to 8.0 cm?

Answer 5

0.25

Question 6

Where should the column element, hexane, be disposed?

Answer 6

non-halogenated waste container

Question 7

The phrase “like dissolves like” is often used in chemistry. What does the phrase mean?

Answer 7

non-polar compounds dissolved in non-polar solvents

Question 8

8 of Nick’s Lab 5 quiz

Answer 8

sdf

Question 9

! Which of the following combinations of solvents would be good for an extraction?

Answer 9

ether and water

Question 10

When preparing a gravity chromatography column, which of the following practices should be followed?

Answer 10

all of the above

Question 11

! Like the experiment last week, today you will perform a liquid-liquid extraction. The organic solvent you will use is hexane (“hexanes” to be specific…). After the hexane layer is separated, you will treat it with anhydrous sodium sulfate. How can you tell when you have added enough?

Answer 11

You add just enough Na2SO4 until some of it does not clump upon addition.
NOT you add the Na2SO4 until it all clumps in the bottom of the flask

Question 12

Q 7 & 8 of Uria’s Spinach Lab Quiz

Answer 12

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Question 13

Where should the column eluent, hexane, be disposed?

Answer 13

non-halogenated waste container

Question 14

The first step of today’s experiment is to grind spinach leaves in acetone with a mortar and pestle. The purpose of this step is to:

Answer 14

solubilize the organic plant pigments in the spinach leaves