Using indicators to determine acids, bases, and salts

In summary, the student forgot to add HCl to the solution and assumed that since the concentration of H+ ions increased, the solution would become more acidic and change colors. However, because the student did not specify the concentration of the HCl solution, we cannot say for sure what would happen.
  • #1
ctamasi
27
0
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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  • #2
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.
 
  • #3
Sounds like antacid titration, which makes me a little doubtful about the story...

--
methods
 

What are indicators and how do they work?

Indicators are substances that change color in the presence of acids, bases, or salts. They work by undergoing a chemical reaction with the substance they are detecting, which causes a visible change in color.

How can indicators be used to determine if a substance is an acid, base, or salt?

Indicators are used in a process called titration, where a known amount of the indicator is added to a solution of the substance being tested. The indicator will change color when it reaches the endpoint, which can then be used to determine the acidity, basicity, or neutrality of the solution.

What are some common indicators and their colors for acids, bases, and salts?

Some common indicators include litmus paper (red for acids, blue for bases), phenolphthalein (colorless for acids, pink for bases), and methyl orange (red for acids, yellow for bases). However, the specific color changes may vary depending on the concentration and strength of the solution being tested.

Can indicators be used to determine the strength of an acid or base?

Yes, indicators can be used to determine the strength of an acid or base by comparing the amount of indicator needed to reach the endpoint. A stronger acid or base will require less indicator to reach the endpoint, while a weaker acid or base will require more.

Are indicators the only way to determine the acidity or basicity of a substance?

No, there are other methods such as pH testing, which measures the concentration of hydrogen ions in a solution, and conductivity testing, which measures the ability of a substance to conduct electricity. However, indicators are a simple and commonly used method for determining the acidity, basicity, or neutrality of a substance.

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