Why can either phenolphthalein or methyl orange be used for an HCl-NaOH titration, but only phnolphthalein is suitable for an acetic acid-NaOH titration?

Sol: for a while,I misunderstood the question and suggested that Phenol. has a wider array of pH. But then both can be used for and HCl-NaOH. I can't see any other reason but to compare the solution changes (-1<pKa>+1.

P.S. I found that the pH of methyl orange ranges from 3.1 - 4.4 pH whereas, phenol. is 8.2 - 10. I know that in acidic solution, Phenol is colorless, so I imagine phenolphthalein is more appropriate for HCl-NaOH titration because it will change color. It's perfect for this type of titration??

Your reasoning is incorrect. Did you not see the post in which I answered this question. It is the one involving how to draw a graph to show the points on the titration curve for acetic acid vs NaOH and HCl vs NaOH and where the indicators change in relation to the end point for each titration. I can't find it now but look through your notes. It may have been another student but I think you were the one. If you can find it then tell me what you don't understand about my instructions for drawing the graph and perhaps we can get through another one together. By the way, phenolphthalein changes from approximately 8.3 to approximately 10 or about 9 as a mid-point. The equivalence point for HCl vs NaOH is 7.0 and the equivalence point for acetic acid vs NaOH is close to 9. The range for methyl orange you found is ok.

I apologize for the misunderstanding. Let me clarify the reasons why either phenolphthalein or methyl orange can be used for an HCl-NaOH titration, but only phenolphthalein is suitable for an acetic acid-NaOH titration.

In an HCl-NaOH titration, both phenolphthalein and methyl orange can be used as indicators because the pH range over which these indicators change color is suitable for this titration. The HCl and NaOH reaction occurs at a pH around 7 (neutral pH), so both indicators will change color close to the equivalence point of the titration.

On the other hand, an acetic acid-NaOH titration involves a weak acid (acetic acid) and a strong base (NaOH). The equivalence point of this titration occurs when the amount of acetic acid is fully neutralized by the NaOH, which means the resulting solution will be basic. Phenolphthalein, with its color change in the pH range of approximately 8.3 to 10, is suitable for this titration as it will change color near the equivalence point. Methyl orange, on the other hand, has a color change in the pH range of approximately 3.1 to 4.4, which is not optimal for detecting the equivalence point of an acetic acid-NaOH titration.

Therefore, the choice of indicator depends on the specific titration being performed and the pH range over which the indicator changes color.

I apologize for any confusion, but as an AI, I don't have access to your previous posts or any notes you may have. However, I can still explain why phenolphthalein or methyl orange are suitable for certain titrations.

Phenolphthalein is a commonly used indicator for acid-base titrations. It changes color over a pH range of approximately 8.3 to 10, with a midpoint around pH 9. This makes it well-suited for titrations involving a strong acid (HCl) and a strong base (NaOH) because the equivalence point, where the moles of acid and base are stoichiometrically equivalent, occurs around pH 7. At the equivalence point, the solution is neither acidic nor basic, so the color change of phenolphthalein provides a clear visual indicator.

Methyl orange, on the other hand, has a different color change range. It changes color from red at pH below 3.1 to yellow at pH above 4.4. This range is suitable for titrations involving weak acids, such as acetic acid (CH3COOH), which has a pKa of around 4.75. In this case, the equivalence point occurs at a pH close to the pKa of acetic acid, which is around 4.75. Therefore, the color change of methyl orange can be used as an indicator for this titration.

In summary, phenolphthalein is suitable for HCl-NaOH titrations because its color change occurs at a pH range above the equivalence point, while methyl orange is suitable for acetic acid-NaOH titrations because its color change occurs around the equivalence point.

yo what's the diference between phoenophyltlein and methyl orange in terms of titrating