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Making Soap and evaluating Soap vs. Detergent Materials: Cooking oil NaOH Solution (25% NaOH in water) Ethanol Saturated NaCl solution “Hard” water Litmus paper Mazola® cooking oil Dish detergent Safety – goggles and aprons. Be careful with hot oil and with 25% sodium hydroxide. Wash off skin promptly. Adding liquids to oil when hot may cause foaming and splashing. Part 1 – Making soap Measure out all ingredients first. When you have the NaOH, the ethanol, and the NaCl solution ready, put 15 ml of cooking oil into a 250 ml. beaker. Add 15 ml of NaOH solution and 15 ml of ethanol. Heat on the hot plate and stir until there are no layers and the soap is a uniform light tan. Towards the end of the reaction, the soap may foam up – be careful. Have your beaker tongs ready if you need to take the beaker off. Pour the soap into 300 ml of NaCl solution and stir well – soap should separate out. Strain through paper towel folded like filter paper in a funnel, rinse with a small amount of cold water and save the solid soap. Part 2 – soap vs. detergent We will compare soap and detergent for acidity or basicity, ability to disperse oil, and ability to clean in hard water. Dissolve 1 g of your soap in 50 ml. distilled water. In a separate container, dissolve 1 g of dish detergent in 50 mL of water. Half-fill three test tubes with each solution (~10 mL). Test one sample of each solution with litmus paper for acidity or basicity. Add 5 drops of cooking oil to one pair of tubes and shake – note differences in how well the oil is dispersed. What do you think this means about the cleaning capability of each? Using the second pair of tubes, add ~5 mL of “hard” water (containing Ca Cl2) and shake. What differences do you see? Calcium ions make water “hard”. What cleaning agent would be most effective in “hard” water? To the third set of 2 test tubes, add 5 ml of tap water instead of lime water; shake. What do you conclude about the hardness of our lab water supply? Write up a lab report summarizing your observations and conclusions. Construct a data table to record the results of your tests on various soaps and detergents. What would be the best way to lay out such a table?
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