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Virtual Lab Experiment
Chocolate is a popular snack throughout South America, North America and Europe. In addition
to its high energy content (33% fat and 47% sugar) chocolate packs an extra punch with the
stimulant caffeine and its biochemical precursor theobromine. Theobromine comes from the
Greek word meaning food of the gods and it is a diuretic, smooth muscle relaxant, cardiac
stimulant, and vasodilator. Caffeine is a central nervous system stimulant.
Too much caffeine is harmful for many people, and in a small fraction of the population even
small amounts of caffeine cannot be tolerated. How much caffeine is in a chocolate anyway?
And how does that amount of caffeine compare with the amount of caffeine found in a cup of
regular coffee?
For this thought experiment you will design an analytical chemistry method using equipment and
reagents selected from a master list (see below). The goal is to determine the amount of
caffeine in a regular size chocolate bar and an 8 oz. cup of coffee. The second goal is to
determine if coffee and chocolate have the same amount of caffeine per serving or not. You
need to describe in detail the following
1. A hypothesis
2. A very detailed step-by-step experimental protocol that includes chemical standards and
calibration curves to measure the amount of caffeine & theobromine in the samples. The
experiment is designed using some (not all!) reagents and equipment provided in the
master list below.
3. Two fictitious data sets (one for a chocolate bar and one for coffee) which you decide will
either support or refute your hypothesis
4. Statistical analysis of the fictitious data
5. A clear, balanced conclusion
Master List of reagents and equipment
Lab notebook, pen (not pencil!) and scotch tape
Computer running Windows 7 with Microsoft Excel 2010 and Microsoft Word 2010
1 regular sized dark chocolate bar
1 8 oz. cup of regular brew coffee
Ceramic mortar and pestle
Electronic analytical balance capable of measuring mass down to 0.10 mg
5, 10, 25, 50 and 100 mL burets
1,2,5,10,25,50,100,200,250,500,1000, & 2000 mL volumetric flasks
0.2-2, 1-10, 2.5-25, 10-100, & 100-1000 uL adjustable micropipette with matching disposable
1,10,50,100 & 500 uL Hamilton syringes
Fritted-glass funnel with electronic air pump
Conical funnel and filter paper
Syringes and 0.45 micrometer filter
50, 100, 500 & 1000 mL beakers
50,100,500, & 1000 mL Erlenmeyer flasks
Vacuum desiccator
A copious supply of tap water
A copious supply of double distilled water
Hot plate
Pure standard of 50% caffeine (w/v) in water
Pure standard of 50% theobromine (w/v) in water
500 mL container of petroleum ether
Centrifuge with disposable centrifuge tubes
Chromatography pump with UV detector
SiO2 solid phase matrix column
C18 solid phase matrix column
Sephadex G-10 size exclusion column, Sephadex G-25 size exclusion column, Sephadex G-50
size exclusion column, Sephadex G-100 size exclusion column
chromatography column packed with anti-caffeine antibody coated beads
acidic solvent (79 ml water: 20 ml methanol: 1 ml acetic acid)
basic solvent (79 ml water:20 ml methanol: 1 ml NaOH)
phosphate buffered saline, pH = 7.4
Of course you may use the internet and primary literature to help you design your scientific
protocol. Your major challenge is taking the time and mental effort to address every aspect of
the experiment that you can try to anticipate potential challenges, inefficiencies, sample loss
and loss of analyte. The more detailed and comprehensive you are in your description the
Dont underestimate the fictitious data set you are going to generate for this project. Based on
your internet research you need to make the data realistic. Once you have the data you are
going to need to use Excel to do statistical analysis. You will also need to be cognizant of the
number of significant digits. Dont forget to show standard deviations for your mean values and
explain to me the rationale you used to decide which statistical method was best for comparing
the chocolate vs. the coffee data.
This project is due no later than the last day of class.
Feel free to contact me at if you have questions. My cell phone is 858245-7158


Solution ID:351186 | This paper was updated on 26-Nov-2015

Price : $60