Sodium Hydroxide (NaOH) solution is delivered from the volumetric burette (on the left) into an erlenmeyer flask (right). The flask contains 40.0 mL of Hydrochloric Acid (HCl) solution. At the beginning of each video, the lab technician also adds a few a few drops of phenolphthalein color-indicator to the HCl solution. A)Write the chemical formula for this reaction. NaOH + HCl → NaCl + H2O

B)What does the color change tell you about the pH of the solution?

C)In science, we like to develop explanations that we can use to predict the outcome of events and phenomena. Try to develop an explanation that tells how much NaOH needs to be added to a beaker of HCl to cause the color to change. Your explanation can be something like: The color change will occur when [some amount] of NaOH is added because the color change occurs when [some condition]. The goal for your explanation is that it describes the outcome of this example, but can also be used to predict the outcome of other examples of this phenomenon. Here's an example explanation: The color of the solution will change when 40 ml of NaOH is added to a beaker of HCl because the color always changes when 40ml of base is added. Although this explanation works for this example, it probably won't work in examples where the flask contains a different amount of HCl, such as 30ml. Try to make an explanation that accurately predicts the outcome of other versions of this phenomenon.

D)In the next section, you will watch a video that shows NaOH with a concentration of 0.2M added to 40ml of HCl, also with a concentration of 0.2M. Use the explanation you wrote in the previous question to predict how much base will have to be added to cause the color to change. Your prediction should be like this: The color change will occur when [your predicted amount of NaOH] is added because [state the explanation you wrote above].