CHEM 131L Principles of Chemistry I Laboratory
Density of an Alcohol
Remote Instruction Version
Introduction
In this virtual lab exercise, you will do an experiment in the Virtual Chemistry Laboratory (VCL). You will
not be given a specific procedure to follow for these experiments; instead, you will design your own
experiment and will determine the procedure necessary to accomplish the goals of the experiment. You
must record your steps and data in an organized fashion. You must show all calculations for full credit.
Background and Procedure
A traditional way of determining the concentration of alcohol in alcoholic beverages is by measuring the
density of the solution, since these two characteristics of the solution (density and percent alcohol) are
elated. This is a convenient determination method because it is low cost and can be done quickly.
Use the information provided in the virtual lab to determine the linear equation describing the
elationship between density and percent alcohol, and determine the percent alcohol in Alcoholic
Beverage A and Alcoholic Beverage B. To determine the linear equation, you will need use Microsoft
Excel or Google Sheets to prepare a graph of density versus percent alcohol. You will use water, 1.00 M
alcohol, and 70.0% alcohol to provide the data for your graph.
To solve this problem, keep the following points in mind:
• Density and percent alcohol have a linear relationship; that is, they are related to one another
y a linear equation of the form y = mx + b, where m is the slope of the line and b is the y-
intercept.
• A 1.00 M solution of alcohol is equivalent to 4.75% alcohol.
• Use 3 significant figures and consider the 70% alcohol solution to have a concentration of 70.0%.
Record your procedure for each step that you perform. Write the procedure as if you were performing
this experiment in a laboratory with real materials. Your procedure should be complete enough that
another student could use your steps to perform the experiment using no additional information.
Record your data in a separate section. Make sure you follow rules for significant figures throughout
your calculations, and show all data and calculations in separate sections. Turn in a copy of the graph
you produced from your spreadsheet. The graph should include properly labeled axes, a caption, the
curve fit, and the curve fit equation and R2 value.
In addition, please write a one-paragraph conclusion to your experiment. The required format for the
conclusion follows.
To access the Virtual Laboratory:
1. Go to http:
chemcollective.org and click on Virtual Lab to the upper right side of the screen under
Quick Links.
2. Click on File, then Load an Assignment.
http:
chemcollective.org
2
3. Click on Molarity and Density to expand that section. Then scroll to the bottom and click on Alcohol
Density Problem.
Everything else you will need is available on the left side of the screen under one of three tabs:
Solutions, Glassware or Tools. Clicking any one of those will give you a list of choices. You might have to
expand a section to see all of the options. When you find what you want, you can click the name of the
item to add it to the workbench, which serves as the main area of the virtual lab. In this experiment you
will choose the size and type of glassware that you use.
When you click on a container on the workbench with a chemical in it, you will see an Information bar
on the left side that provides specific information about that solution or substance. When you have
clicked on a container on the workbench containing a solution, you can control what information is
displayed by clicking on View at the top of the screen. A drop-down will appear with choices that you
can check or uncheck. For this experiment, uncheck Solution Properties.
Conclusion
The conclusion is a double-spaced, 1-paragraph summary XXXXXXXXXXwords) of the experiment in which
you:
1. Summarize, in one or two sentences, the overall goal of the experiment.
2. Summarize, in one or two sentences, the overall procedure used to accomplish the goals.
3. Present your final results. Note that the results are not the same thing as the data that is
collected. You do not need to present your data in the conclusion.
4. Use your results and observations to comment upon sources of unavoidable e
or in the
experiment. Note: human e
or is not an acceptable answer since it is avoidable.
5. Was the calculated concentration of the alcohol reasonable?
6. What improvements, if any, could you make to the procedure if you were completing this
experiment in an actual laboratory?
In scientific writing, third-person, passive voice is used. This keeps the focus on the experiment, rather
than experimenter. For example, “A 5-mL volume of solution was poured into an evaporating dish” is
proper. Writing “We poured a 5-mL volume of solution into an evaporating dish,” is improper.