1. Explain why sodium polyacrylate powder turns into a gel when mixed with water

Question

1. Explain why sodium polyacrylate powder turns into a gel when mixed with water.

2. Ion hydration is an important part of the gel dissolving process. Draw a labeled hydration spheres for the sodium and chloride ions. Label and diagram any intermolecular forces.

3. How could you regenerate the sodium polyacrylate powder?

4. Sodium polyacrylate is commonly found in disposable diapers. Explain why more sodium polyacrylate is required to absorb urine (urine contains salts, urea, and other dissolved compounds) as compared to pure water.

5. Although different acrylic polymers have structural similarities, why do they have a range of properties?

Explanation / Answer

1) The polymer is a superabsorbent polymer and it absorbs 100-1000 times it's weight of water and therefore it forms a gel. In the powder form, the sodium ions which are positively charged bind tightly within a cage formed of polyacrylate unit chains, kept closed by negatively charged carboxyl groups which are sort fo hanging off the polymer backbone.On addition of water, the sodium ions are replaced by positively charged hydrogen ions in the water, the sodium ions are then freed and move out. The tightly organised polymer chains begins to unravel. The chains do not completely separate and dissolve. A stiff gel is formed by the swelling of the chains by absorbing the water

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