Using indicators to determine acids, bases, and salts

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Discussion Overview

The discussion revolves around a lab scenario involving the addition of hydrochloric acid (HCl) to a solution containing milk of magnesia and universal indicator. Participants explore the expected color change of the solution upon the addition of HCl, considering the implications of acidity and the specific concentrations involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the lab procedure and hypothesizes that adding HCl will lead to a color change in the universal indicator from purple to a lighter color due to increased acidity.
  • Another participant emphasizes the need for specific concentrations of both the milk of magnesia and HCl to accurately predict the outcome, noting that the information provided is insufficient for a definitive answer.
  • A third participant expresses skepticism about the scenario being described, suggesting it resembles an antacid titration but questioning the validity of the details shared.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the expected outcome of the experiment, as there are competing views regarding the necessary concentrations and the validity of the described lab scenario.

Contextual Notes

The discussion highlights limitations in the information provided, particularly regarding the concentrations of the substances involved, which affects the ability to predict the solution's behavior accurately.

ctamasi
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Hey, I just got out of my lab at school and just realized that me and my professor made a mistake. He marked my lab complete, and I also thought it was complete, however, I just realized that there was something missing. The problem is that I can't go back into the lab to try it out again. Its not a big deal I just want to know what would have happened.

This is the problem:

In the lab, I added 200mL of water to a 400mL beaker, then I placed it on a magnetic stirrer and added a couple drops of universal indicator, then I added a milk of magnesia tablet. Then I had to note the color changes. Once the tablet completely dissolved, the solution turned purple. Now, the next step was to add a couple drops of HCl to the purple solution. This is the step I forgot, and somehow my prof didn't notice, but I need to know what would happen? Like I said, the lab is already done, however, I don't want this to pop up on the exam or something. So, to recap, my question is, what will happen to the purple solution after I add some HCl?


My attempt at a solution:

Now, my assumption is that the solution will become more acidic since the concentration of H+ ions increases:

H2O + HCl --> H+ + Cl-

So, since I was using universal indicator, I would assume that as the purple solution becomes more acidic, the color of the solution will change from purple to some lighter color like orange or even red.

Can anyone help me out? Thanks a lot.
 
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We really do not know what will happen unless we know the concentration of Milk of Magnesia and the amount used and the concentration of the hydrochloric acid used. "Milk of Magnesia Tablet" is not something for which most people know the concentration which is why we would need to know this. We can guess that "two drops" of HCl means 0.10 ml, but we are not given the concentration of the HCl solution.
 
Sounds like antacid titration, which makes me a little doubtful about the story...

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