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Lab 2: What’s the Concentration of Kool-Aid?

Purpose: Determine the concentration (molarity) of properly made Kool-Aid.

Method: Make three solutions of Kool-Aid with different concentrations and taste them to decide which is the correct concentration. You will prepare 0.1 L of each of the following Kool-Aid solutions: 0.1 M, 0.4 M, and 0.7 M.

Materials:

Kool-Aid PowderVolumetric Flask (the size will vary between 0.1 L and 1 L)

WaterBalance

Paper Dixie Cups

Procedure:

1. Calculate how much solid Kool-Aid you will need to make 0.1 L of each solution. (Hint 1: Kool-Aid is mostly sugar (C6H12O6), so you can assume that the “molar mass” of Kool-Aid is the same as the molar mass of sugar.) (Hint 2: “What you know” is the volume – 0.1 L)

Show all of your calculations below. Circle or box the answer for each part.

The “molar mass” of Kool-Aid (C6H12O6):

Mass of Kool-Aid needed for 0.1 M solution (HINT – Multiply 0.1 M by 0.1 L to get moles of Kool-Aid needed):

Mass of Kool-Aid needed for 0.4 M solution:

Mass of Kool-Aid needed for 0.7 M solution:

2. Obtain a volumetric flask. The size of this flask will vary between 0.1 L and 1 L. If you get a size that is not 0.1 L, then redo your calculations from the pre-lab so that you know how much Kool-Aid powder you will need.

3. Mass out the correct amount of solid Kool-Aid needed to make the 0.1 M solution. Put your cup on the balance, set the mass to zero, and put the correct mass of Kool-Aid for the 0.1 M solution in the cup. If you make a mess, make sure you clean it up before you leave the balance station.

4. Obtain a wash bottle. Fill the volumetric flask with water until it is almost filled to the line. Once you get close to the line, begin using your wash bottle to fill to the line. Fill the volumetric flask until the meniscus touches the line. Mix the solution thoroughly.

5. Once you complete your 0.1 M solution, pour at least 250 mL into a beaker and place it to the side and repeat steps 2 – 5 to make your 0.4 M and 0.7 M Kool-Aid solutions. Right down your observations of each solution in the area below. DO NOT DISPOSE OF ANY SOLUTIONS.

6. Calculate the % sugar in each of the three solutions that you just made. Use the mass of Kool Aid that you just massed out. This is the msolute. The density of water is 1.00 g/L, so if you have 0.1 L of water then you have 100 g of solvent. This is your msolvent. Remember:

msolute + msolvent = msolution

Check these answers with Mr. Astor before you proceed to the next step.

0.1 M:

0.4 M:

0.7 M

7. Use a graduated cylinder to measure 100 mL of 20% sugar solution.

8. Place an empty 250-mL beaker on the balance and press the “tare” or “rezero” button. If you do not have access to an electronic balance, a triple-beam or similar balance can be used.

9. With the beaker still on the balance, carefully pour your 100 mL sample of liquid into the beaker.

10. Record the mass of the liquid in Data Table 1 in the results section.

11. Dispose of your liquid properly then rinse and dry the beaker and the graduated cylinder.

12. Calculate the density of your sugar solution by the equation:

Record the value in Data Table 1.

13. Repeat Steps 7-12 for the twoother sugar solutions

14. Repeat steps 7-12 for a pure water sample. Measure out 100 mL and complete the same steps as you did for the Kool Aid solutions. This is your 0% sugar solution.

15. Obtain a solution of unknown concentration. Repeat steps 7-12 to determine the density of the unknown solution. Record the mass and density in the data table.

15. Dump leftovers in the sink and throw away used cups.

Data and Results:

Molarity (M) / Mass of Kool Aid Powder Used (g) / % Sugar Solution / Mass of Solution (g) / Density of Solution (g)
0.1
0.4
0.7
0%
Unknown Sugar Solution

Calculations (To Do In Class Wednesday):

11. Use Microsoft Excel to plot density on the y-axis vs % sugar on the x-axis for the 0%, 5%, 10%, and 20% sugar solutions. Use a ruler to draw a straight “best-fit” line for your four data points. The best-fit line helps compensate for experimental error and is sometimes called a calibration curve. An example of a graph with a best- fit line is shown below

12. Use your best-fit line to estimate:

a. The density of a 15% sugar solution. Record this value on Excel.

b. The density of a 25% sugar solution. Record this value on Excel.

c. The sugar concentration of your unknown solution. Record these data below.

LABS AND PROJECTS