Determining the densities of known sugar solutions draw up

Question

 

Lab: Determining the Amount of Sugar in Soda

Pre-Lab Assignment

1. Define "tare"

2. Explain the difference between an independent variable and a dependent variable on a graph.

3. Which variable is the independent variable for the graph you will be preparing in Step 16?

4. A student prepared a solution of sodium chloride (NaCl) in distilled water by dissolving 1.05 g of NaCl in about 50 mL of water. The mass of the final solution is 51.98 g. Determine the mass percent NaCl in the solution.

5. A student uses a volumetric pipet to transfer 10.00 mL of the NaCl solution as described question 3 to a beaker. The mass of this volume of solution is 10.08 g. Determine the density of the solution.

6. The student prepared two more NaCl solutions in water. The densities of these solutions, as well as distilled water is determined. The results are summarized in the table below. Record your calculated results from question 3 & 4 in this table.

	water	solution
		1                      2                        3
mass percent NaCl, %	0		4.07	6.16
density, g/mL	0.993		1.021	1.034

Prepare a graph of density versus mass percent NaCl for these solutions, either using a computer spreadsheet program or draw by hand. Determine the trend line equation by either drawing the best straight line through data points and calculating slope and y-intercept values or by using a computer spreadsheet program to determine the equation of the trend line. Attach your graph and record the equation of the trend line below (be sure to define x and y in terms of the variables graphed):

7. The student obtains an unknown NaCl solution and determines that its density is 1.015 g/mL. Determine the mass percent NaCl using the trend line from question 5.

Procedure: Record all masses to the nearest milligram (0.001 g).

A Determining Mass % of Known Sugar Solutions

1. Obtain a clean, dry small bottle, and label it "A". Tare the bottle on the balance.

2. To make solution "A," place about 2.5 g of sugar into the bottle. Record the actual mass to the nearest milligram (0.001 g) for the amount of sugar added in Table 1.

3. Using a graduated cylinder, transfer approximately 48 mL of distilled water to the bottle. Record the total mass of the solution in Table 1.

4. Cap the bottle, and shake thoroughly until all the sugar has dissolved.

5. Repeat the procedure above by using the other sugar solutions: Solution "B" will have about 5.0 g of sugar; Solution "C" will have about 7.5 g of sugar.

6. For each solution, calculate the mass percent sugar according to Equation 2. Record in Table 1.

7. Solution "D" is pure water. Pour about 50 mL of distilled water into a small bottle. Label the bottle "D." This solution is your 0.00% sugar solution.

B Determining the Densities of Known Sugar Solutions

8. Tare a clean dry 50-mL beaker.

9. Draw up enough solution D to half fill a clean, dry 10-mL volumetric pipet. Use this solution to rinse the inside of the pipet. Allow the rinse solution to drain into a 150-mL beaker, labeled "Discard Solutions."

10. Use the rinsed 10-mL volumetric pipet to transfer 10.00 mL of solution D to the tared 50-mL beaker. Measure and record the mass to the nearest milligram (0.001 g) in Table 1.

11. Pour the contents of the beaker into the drain, diluting with a large amount of running tap water. Wash the beaker and rinse with distilled water for reuse.

12. Repeat the procedure above at least two more times, so that there are 3 determinations that agree within the limits specified by your laboratory instructor.

13. Repeat steps 8-12, using Solutions A, B, and C.

14. For each solution (A-D), calculate the Average Mass of 10.00 mL of Solution and record in Data Table 1.

15. For each solution (A-D), calculate the Average Density of the Solution and record in Data Table 1.

16. Graph your results by plotting the Average Density of the Solution vs. Mass % of Sugar using Logger Pro. Keep in mind the independent variable (x-axis) is the Mass % and dependent (y-axis) is Average Density. Do not start your y-axis at 0. Instead, select y-axis scale units so that the lowest value is slight below the Average Density of Solution D, and the highest value is slightly above the Average Density of Solution C. Your x-axis should run from 0.00 to 20 Mass % Sugar. Perform a linear regression analysis for your graph. Record the equation for the resulting trend line and correlation value on your Data Sheet.

C Finding the Density of Soda or Other Sugar Containing Beverage

17. Obtain two beverage samples from your laboratory instructor. Record the identification code or names of your two samples and the amount/serving of sugar and serving size in Data Table 2.

18. Repeat steps 8-15 using each beverage sample, record results in Data Table 2.

19. Using either your graph or the trend line equation, determine the mass percent sugar for each of your beverages. Record results in Data Table 2.

20. Pour the contents of your "Discarded Solutions" beaker and any remaining solutions or samples into the drain, diluting with a large amount of running tap water. Wash all containers well and clean up benches and balance area.

21. Using the graph that you have completed in Part B, determine the amount of sugar in your soda or beverage sample. Record in Data Table 2.

Data Sheet:

Data Table 1. Determining Mass Percent & Average Densities of Known Sugar Solutions

Solution	Mass of Sugar	Mass of Solution	Mass Percent Sugar	Mass of 10.00 mL of Solution (g) Determination			Average Mass of Solution	Average Density of Solution (g/mL)
	(g)	(g)	(%)	1	2	3	(g)
A
B
C
D	0.000 g		0.00%

Graph:

1. Using Logger Pro, input the data from Mass Percent Sugar (%) and Average Density of Solution (g/mL). Input the data so that the Mass % Sugar is the independent variable (x-axis) and the Average Density of each solution as the dependent variable (y-axis).

2. Be sure to label the axes and title the graph appropriately.

3. Perform a linear regression analysis. Include the equation of the trend line and correlation value.

density, g/mL = (_______________) (mass percent sugar, %) + ________________

slope y-intercept

correlation value: _________________

Data Table 2. Determining Amount of Sugar in Soda or Other Sugar Containing Beverage

Identification Code or Name of Beverage	Serving Size	Calories/Serving	Mass of 10.00 mL			Average Mass of Beverage	Average Density of Beverage (g/mL)	Mass Percent Sugar*
	(oz & mL)		of Beverage (g)			(g)		(%)
			Determination
			1           2           3

*Determine using the trend line equation. Use space below for any calculations.

Post Lab Assignment:

1. a) Using the "Nutrition Facts" label on the soda container, calculate the Calorie content per milliliter serving for each of your beverage samples, and create a table showing the mass percent sugar and Calorie/mL values for each of your three beverage samples.

b) Is the sugar content proportional to the caloric content of the beverages? Discuss any similarities or differences observed.

2. Determine the percent error for your average density of water. The accepted value for the density of water is 0.998 g/mL (d_accpeted) at 22 ^oC. The percent error can be calculated according to Equation 3 where d_experimental is your average density for solution D:

Equation 3

percent error, % = |(d_accpeted - dexperimenta) / d_accpeted| x 100%

3. Each of the soda samples were degassed prior to the analysis performed in this lab. Do you think the results of this lab might have been different if the soda was not de-gassed? How might your results been different?

4. It is estimated that the average American drinks 53 gallons of soda in a year. Using the average density you calculated for one of your soda samples determine the amount of sugar (in grams) this corresponds to. 1 US gallon = 3.7854 liters

 

 

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