SUBBU ONLY

CAN YOU DO THIS ONE ?

QLP Module – Density

1. Visit the website for the ChemCollective Virtual Lab (http://collective.chem.cmu.edu/vlab/vlab.php).

After the program loads, select “File” and click on “Load Homework”. You will scroll all the way down

to the “Online Repositories”.

2. Double click on the “Online Repositories” and click on the icon next to “SINCLAIR.EDU”. Click on the

icon next to “Che126” and double-click on “Alcohol Density Problem”.

3. On the left panel, double click on “Problem Description” for an overview of the activity and the

procedure to follow. You can switch between the “Workbench” and the “Problem Description” by

selecting them using the tabs at the bottom of the display.

4. To toggle between the virtual bench and the problem description, simply click on either one at the bottom

of the blue screen.

The Lab

A. Take out three 250 mL Erlenmeyer flasks by clicking on the third icon to the left of the workbench (“glassware”).

Take the scale out by clicking on the last icon (“tools”). Drag into the bench, the water, the 1M alcohol solution,

and the 70% by mass alcohol solution.

B. Place one of the empty Erlenmeyer flasks on the scale by dragging it on top of it. The scale should go

from a reading of 0.0000g to something else. Click on “TARE” to clear the mass reading. This will

allow you to read the mass of the liquids being poured, without including the mass of the flask itself.

glassware

tools

QLP Module – Density

C. Drag the 70% by mass Erlenmeyer flask containing the alcohol near the top of the Erlenmeyer flask.

You should notice that it tilts and at the bottom of the screen a box appears to input volume. Transfer

25.0 mL of the 70% alcohol solution to the flask on the scale by clicking on “POUR” after typing in

the volume to transfer. Drag the flask with the 70% by mass alcohol solution away and place it

somewhere else on the virtual bench. Record the mass of the 25.0 mL of the 70% by mass solution.

D. Take out a 250 mL beaker using the glassware icon and poor some water in it by dragging the beaker

close to the water container. You should notice the input box on the bottom of the screen to indicate

the volume you wish to transfer. Follow the same procedure as in C.

E. Take the 250 mL beaker with the water near the flask on top of the scale and when it tilts, transfer

25.0 mL of water. Record the mass reading on Table I (see last page). You can discard this

solution

by selecting the flask and hitting the delete key on your keyboard.

F. Calculate the mass percent of alcohol in this solution. Let’s review how we do that!

In a 70.0% by mass alcohol solution there are 70.0 g of alcohol per 100.0 g of solution. The data gathered by

us shows a mass of 22.0412 g for the 25.0 mL of this solution. That means we had,

Type in volume to transfer

QLP Module – Density

15.42884 g of solute. The total mass of the solution after adding the 25.0 mL of water was 47.0412 g. We can

calculate the new mass percent of alcohol as,

Assuming volumes are additive, the density of the solution can be calculated using the mass of the solution

and dividing by the total volume of the solution.

G. Prepare and record the data for eight additional solutions in which the mass percent of the

alcohol

varies from 0% to 50%. Use clean Erlenmeyer flasks for each solution.

Table I: Experimental data on mass and volume of a series of alcohol-water mixtures

Volume of

70%

alcohol
solution

(mL)

Mass of

the 70%

alcohol
solution

(g)

Volume of

water

added (mL)

Mass

percent of

alcohol in

the new

solution

Total

volume of

solution
(mL)
Mass of

solution (g)

Density of

solution

(g/mL)

Example:

25.0

22.0412

25.0

32.8%

50.0

47.0412

0.941

H. Use the data you collected to prepare a graph of density (y –axis) as a function of mass percent of the

alcohol (x-axis). Add a linear trendline to your graph as you did on Part B of this module.

I. You will notice that there are two alcoholic beverages on stock (Alcoholic Beverage A and Alcoholic

Beverage B). Select the two containers and drag them to the virtual bench. Use a clean 250 mL

Erlenmeyer flask and place it on the scale, tare it, pour 50.0 mL of Alcoholic Beverage A into it and

record the mass. Do the same with Alcoholic Beverage B using a clean Erlenmeyer flask. Determine

the density of the alcoholic beverage and using your graph, estimate the percent by mass of alcohol in

QLP Module – Density

it by looking at the point at which it intercepts the linear trendline and reading the mass percent of

alcohol it corresponds to.

Lab Report

The report must contain the following parts:

 Introduction – What is the purpose of this lab? How was the data collected?

What data was collected?

 Sample calculations using your data (only one of each: the calculation of the

mass percent of alcohol for one dilution and the density).

 Table I (Summary of data)

 Graph of density as a function of alcohol content (mass percent)

 Conclusion – Describe how the density of the solutions varies with increasing

mass percent of alcohol, estimate the alcohol percent in both alcoholic

beverages, explain how you estimated the alcohol content in the beverage.

All of these items must be included in a report not to exceed 3 pages when typed in a

12-point font doubled-spaced with 1 inch margins. For comparison, this page has been

written using those settings. You should employ complete sentences and develop the

thesis (the main purpose or goal of this activity) in a logical and sequential manner.

Proper grammar (10%), correct mathematical procedures paying attention to units and

significant figures (20%), tables and graphs labeled and titled (30%), and correct and

complete conclusions (40%) will be evaluated for grading purposes.