User:Elizabeth Ghias/Notebook/Experimental Chemistry/2013/02/11

Experimental Chemistry

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Objective To crosslink the films prepared last class, to test the effects of using a lower molecular weight PVOH on the film, and to prepare a 0.2 M NaOH solution for use next class. Description Crosslinking Determined the concentration of HCl needed, by determining the amount of H+ in the H2SO4 used in previous crosslinking. 20ml of 100% H2So4 in 1 L of H20 was used, assuming complete dissociation 20ml* 1.84g/ml ÷ 98.079g/mol = 0.375moles of H2SO4 ÷ 1 Liter= 0.369 Molar H2SO4 0.369mols of H2SO4/L * 2mols HCl/1mol of H2SO4 = 0.7M HCl → 6ml of 12 M HCl Heat up a solution of 94 mL water and 6 mL 12 M HCl to 70°C Place the film in the solution and heat for 1 hour. Prepare a solution of bicarbonate (1.68 g in 100 mL). At the end of one hour, remove the films from the HCl, rinse with water, then place in the sodium bicarbonate solution for 15 minutes. Then remove the films from the bicarbonate solution and place in water. Leave the films in water until Friday. Preparation of Lower Weight PVOH Films Measured out 6 1 g samples of PVOH (MW = 22,000) Prepared a solution of 0.22 g phenol in 10 mL water. Dissolved the PVOH samples in 30 mL water (in 100 mL beakers) Once the PVOH had dissolved, the corresponding amounts of phenol solution were added (1% film = 1 mL, 0.1% = 0.1 mL, 0.01% = 0.01 mL, 8.5% = 8.5 mL) 1 mL glutaraldehyde was added to each film The solution was allowed to stir and then was poured into an plastic dish and allowed to evaporate until Friday. NaOH Calculations and Preparation need to prepare 50 mL of a 0.2 NaOH solution from a 0.5 N NaOH soln. (0.5 moles/L)(X) = (0.2 moles/L)(0.05 L) → X = 0.02 L = 20 mL Measure out 20 mL 0.50 NaOH Add to 30 mL water Save for use on Friday. Data No data was collected today. Notes Description of Films Prepared Last Class 1% film prepared in Erlenmeyer flask looked the best, was uniform, etc. 0.1% and 9% films were not uniform, had lumps of PVOH The poor quality of the films was attributed to the high molecular weight of the PVOH.