Experimental Procedure

Preparation of the Sucrose Solution

1. The instructor will assign a sucrose concentration of between 5 and 15 % to each lab group. Record the assigned concentration in your data sheet.
2. In the designated space of the data section, calculate the approximate mass of sucrose that is needed to make a 100 g sample of the assigned concentration.
3. Obtain approval of the instructor before continuing.
4. Tare (zero) the scale to be used. Place a 150 mL beaker on the scale and record the mass in your data section.
5. Add the approximate mass of the sucrose calculated to the beaker and record the mass in the data section.
6. Add water to the beaker until you have reached ~100 g of solution (The mass will read the beaker’s original mass + 100 grams). Record the final mass of the beaker, sucrose and water in your data section.
7. You may need to gently swirl or stir to dissolve the sucrose.

Calibration of a 10.0 Graduated Cylinder

10. Record the temperature of the room.
11. Tare a 50 mL beaker on an analytical balance. (The balance should read zero with the beaker on the measuring pan so that the beaker’s mass does not need to be subtracted each time.)
12. Measure exactly 10.0 mL of DI (deionized) water using the graduated cylinder.
13. Transfer the water to the tared beaker and record the mass of the water added.
14. Pour the water down the drain.
15. Repeat this trial five times. Remember to tare the beaker each time it is weighed since it might still contain residual water.
16. Use Table 1 from the Introduction and the temperature of the lab to calculate the volume of DI water actually delivered by your graduated cylinder.

Mathematically Calculating the Density of Prepared Sucrose Solution

1. Tare a 50 mL beaker on an analytical balance.
2. Measure exactly 10.0 mL of the sucrose solution measured in Part A. using the graduated cylinder.
3. Transfer the solution to the tared beaker and record the mass.
4. Pour the solution into a separate beaker. Do not dispose of it yet as you may need it later.
5. Repeat this trial five times. Remember to tare the beaker each time it is weighed since it might still contain residual solution.
6. Use the recorded masses and the volume of the graduated cylinder (calibrated volume from Part B) to calculate the density of the sucrose solution.

Graphically Calculating the Density of Prepared Sucrose Solution

1. For this section students will be gathering information to graph. The graph will then be used to determine the density of the sucrose solution. Unlike Part C, the beaker should not be tared or emptied before adding more solution.
2. Obtain the mass of a clean, dry 100 mL beaker. For this section, do not tare the beaker.
3. Measure exactly 10.0 mL of the sucrose solution measured in Part A. using the graduated cylinder.
4. Transfer the solution to the beaker and record the mass.
5. Do not pour the solution out.
6. Measure another 10.0 mL of the sucrose solution and transfer it to the beaker. Record the mass.
7. Repeat this trial five times.
8. Graph the recorded masses and calibrated volumes in your data Table D.
9. The y axis should be the mass in grams. The y-intercept should be the mass of your beaker. You should scale your axis so that the data takes up most of the space. (Do not start at 0).
10. The x axis should have units of volume in mL.
11. The slope of the data will have units g/mL (and therefore be the density of the sucrose solution.

Experimental Data and Results

A. Preparation of the Sucrose Solution

Before you begin, calculate the approximate mass of sucrose and water needed. Show all work and use the correct number of significant figures to receive full credit.

Assigned Sucrose Solution (%w/w): _______________________

Approximate mass of sucrose to be used: ____________________

Approximate mass of D. I. water to be used: __________________

Record all data from the scale and determine the %w/w of the solution made.

B. Calibration of a 10.0 Graduated Cylinder

Record the temperature of the lab.

Temperature of Lab: _______________________

Density of water at this Temperature according to Table 1 =__________________

Determine the volume of water using the mass of water delivered and the density of water from Table 1.

Be sure to show an example of the calculations necessary to determine the volume of water delivered.

C. Mathematically Calculating the Density of Prepared Sucrose Solution

Show an example of the calculations necessary to determine the volume of water delivered.

D. Graphically Calculating the Density of Prepared Sucrose Solution

In this section you will collect data to graph. You will graph the mass of the solution + beaker vs. the volume of the solution.

Mass of Empty Beaker ___________________

In the space below: plot a graph of mass on the y-axis versus volume on the x-axis. All graphs must have each axis clearly labeled with numbers and units. The graph must have a title and legend. Draw a “best fit” straight line through as many of the points as possible. You should use a ruler to draw the line. This graph should not simply be a “connect the dots” line.

1. Find the slope of this line by using two of the most widely spaced data points you have measured which come closest to the best fit straight line that you have drawn with your ruler. Remember,

[latex]\displaystyle\text{Slope}=\frac{\text{rise}}{\text{run}}=\frac{\Delta{y}}{\Delta{x}}=\frac{\left(y_2-y_1\right)}{\left(x_2-x_1\right)}\\[/latex]

Slope of the line (density): ______________ g/mL

2. Calculate the % Error of the Density of the solution you made by comparing it to the theoretical density in Table 2 from the introduction.

3. Next, observe where the line intersects the y-axis. This number should be close to the mass of the empty beaker containing 0 mL of the solution.

y-intercept of best fit line: __________________ g

4. Calculate the % error comparing the y intercept value compared to the mass of the empty beaker.

Post-Lab Questions

1. Which method that you used for the calculation of density of the sucrose solution is the most accurate, Part C or D? Explain your answer.
2. When performing today’s lab, you measure the temperature of the lab during the calibration of the graduated cylinder. You record the temperature as 2 degrees higher than it actually is. How will this error affect the calculated density (will the resulting calculated density be too high, too low or unaffected)?
3. When making the sucrose solution in Part A you measure the correct amount of sucrose on the scale. However some of the sucrose was spilled on the balance and not into the beaker. How will this error affect the calculated density (will the resulting calculated density be too high, too low or unaffected)?
4. When trying to measure the density of your solution, you do not quantitatively transfer the solution (there is still some in the graduated cylinder when you obtain the volume in Part D). How will this error affect the calculated density (will the resulting calculated density be too high, too low or unaffected)?