1. Chemistry XXI Lab Session 11 How can we characterize the “absorption” capacity of a superabsorbent polymer?

2. Chemistry XXI Your Challenge Imagine that you work for a company that is interested in using superabsorbent polymers, in particular sodium polyacrylate, as ion and molecule “scavengers” for removal of toxic substances dissolved in water. Your task is to design a set of experimental procedures to characterize the capacity of the polymer to absorb a variety of dissolved substances.

3. Chemistry XXI Weak electrolyte Your Tasks In order to accomplish your goals, you have to complete three basic tasks:  Task 1: Determine how the water absorption capacity of sodium polyacrylate varies as a function of sodium chloride concentration.  Task 2: Quantify the mass of copper (in Cu 2+ form dissolved in water) that sodium polyacrylate can absorb per gram of this polymer as a function of time.  Task 3: Pose a research question to investigate in the lab, and design and implement and experiment to answer it.

4. Chemistry XXI Task 1: Your Plans In your groups, share your ideas about how to solve this problem, and come up with a common plan that your group will implement. Once you have a plan, share it with your lab instructor and the rest of the class.  Task 1: Determine how the water absorption capacity of sodium polyacrylate varies as a function of sodium chloride concentration. NaCL (g/L) mL solution/g polymer 010x 1 x 2 EXPECTED OUTCOME

5. Chemistry XXI Available resources:  1.0 g of polymer (0.25 g per test);  10.0 g/L NaCl solution;  Filter papers;  Plastic stirring rod;  Volumetric glassware;  Digital scale. You have 45 minutes Determine how the water absorption capacity of sodium polyacrylate varies as a function of sodium chloride concentration. Your First Challenge

6. Chemistry XXI Present your claims and evidence to the class. Decide as a group which data should be shared to facilitate the analysis. Claims, Evidence, and Reflection  Collectively analyze the data and discuss what they tell you about the absorption properties of the polymer;  Discuss any potential sources of error. NaCL (g/L) mL solution/g polymer

7. Chemistry XXI Results using nanopure water (results with tap water may be half of these values)

8. Chemistry XXI Task 2: Your Plans In your groups, share your ideas about how to solve this problem, and come up with a common plan that your group will implement. Once you have a plan, share it with your lab instructor and the rest of the class. Time (min) Mass Cu 2+ /g polymer 02 4 6 8 10 EXPECTED OUTCOME  Task 2: Quantify the mass of copper (in Cu 2+ form dissolved in water) that sodium polyacrylate can absorb per gram of this polymer as a function of time.

9. Chemistry XXI Available resources:  0.25 g of polymer;  100 mL of 0.05 M Cu(NO 3 ) 2  Tea bag;  Absorption spectrometer;  Stopwatch;  Magnetic stirrer and stir bar;  Volumetric glassware. You have 45 minutes Quantify the mass of copper (in Cu 2+ form dissolved in water) that sodium polyacrylate can absorb per gram of polymer as a function of time. Your Second Challenge

10. Chemistry XXI Present your claims and evidence to the class. Decide as a group which data should be shared to facilitate the analysis. Claims, Evidence, and Reflection  Collectively analyze the data and discuss what they tell you about the absorption properties of the polymer;  Discuss any potential sources of error. Time (min) Mass Cu 2+ /g polymer

11. Chemistry XXI 0.005- C*0.1/0.25 x M(Cu) If A  C

12. Chemistry XXI Task 3: Your Plans In your groups, share your proposed research questions and your ideas about how to find the answer. Select a research question for your group and design a experiment to answer it. Once you have a plan, share it with your lab instructor and the rest of the class.  Task 3: Pose a research question to investigate in the lab, and design and implement and experiment to answer it.

13. Chemistry XXI Available resources:  1.0 g of polymer;  NaCl, Cu(NO 3 )2, Ni(NO 3 ) 2, Co(NO 3 ) 2 solutions;  Solid CaCl 2 ;  FD&C Dye Blue #1 and FD&C Dye Red #40 solution;  Absorption spectrometer;  Stopwatch, etc. You have 45 minutes Implement an experiment to answer your research question. Your Third Challenge

14. Chemistry XXI Present your claims and evidence to the class. Decide as a group which data should be shared to facilitate the analysis. Claims, Evidence, and Reflection List and discuss the specific things that you have learned about the absorption capacity of the superabsorbent polymer investigated in this lab.

15. Chemistry XXI No Report for this Week Your Comments  Discuss in your groups the strengths and weaknesses of this lab, and write down your group suggestions to help improve it.