4 The indicator you will use phenolphthalein turns from colorless to pink at pH

4 the indicator you will use phenolphthalein turns

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4. The indicator you will use (phenolphthalein) turns from colorless to pink at pH ~8. It is very important that the color change is noticed immediately. How would the optical clarity ofthe grape juice affect your experiment and what can be done to enhance the visibility of the color change? Since white grape juice, is clear, with a small tint of green, colors can be faded within, even though the substance would be described as see through the pink color change is very slight. In order to enhance the visibility of the color change, a white piece of paper can be added to the bottom of the beaker where the colors stand out more.5. Given the variety of juice samples, devise a testable question that can be answered by your inquiry into acid content. You may want to think about the characteristics of the juice samples in order to do this (e.g. “light/diet,” store brand vs. national brand, etc.)Does being a “light” white grape juice reduce the acidity level?6. Given your testable question, make a prediction about the outcome? (e.g. Juice A will be more or less ___ because…)Welch’s Light White Grape Juice will be less acidic than other brands, because it containsless sugar and calories.7. Outline a preliminary plan to determine the concentration of acid of various samples of white grape juice to answer your testable question.- Determine pH level of each grape juice brand with pH paper prior.- Assemble titration set up, and place 0.0189 M NaOH in buret and titrate it into 20 mL ofwhite grape solution and add 3 drops of phenolphthalein indicator.- Titrate NaOH until the conical flask solution turns pink and stays pink while stirring. Record volume of NaOH. - Calculate pH of solution after being titratedProcedure1.Acquire all materials needed: Welch’s White Grape Juice, Welch’s Light White Grape Juice, Gerber White Grape Juice, Publix White Grape Juice, Phenolphthalein indicator, beaker, conical flask, titration apparatus.2.With each brands grape juice, use the pH paper to find the pH of each juice, use color keyon pH paper to be accurate. Record the initial pH of the juices in Data Table 1. 3.Assemble the titration setup.a.Using a ring stand, attach a buret clamp to towards the top of the ring stand. Insert the buret to the buret clamp. Add a beaker to the base of the ring stand, and adjust buret height. 4.Create acidic solution to go on conical flask at the base of the ring stand.a.For each brand of the white grape juices, repeat the following steps. b.Get 2mL of pure white grape juice brand, an accurate measure. Then measure out 18mL of deionized water. Combine both mixtures into a cleanconical flask and stir to mix. Add 3 drops of phenolphthalein indicator intothe flask and place under buret with a white piece of paper for distinction.
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a.Rinse out buret with deionized water while the stopcock is closed. Then, drain the water into a beaker out of the buret. Add 2, 5 mL portions of 0.0189 M NaOH into the buret.
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  • Spring '08
  • pH

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