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Which indicator,methyl orange or phenolphtalein will be more suitable to be used to...

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inquire123 | Student | eNoter

Posted January 8, 2013 at 8:53 AM via web

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Which indicator,methyl orange or phenolphtalein will be more suitable to be used to differentiate between an acid and water?Explain your answer.Thanks

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jerichorayel | College Teacher | (Level 1) Senior Educator

Posted January 8, 2013 at 10:03 AM (Answer #1)

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It would be great if we show first the pH range where the color of the solution will change. Consider the following table:

Methyl orange

Color on the acidic side: red
Color on the basic side: yellow
pH range of color change: 3.1-4.4
**meaning, pH greater than 4.4 will show a intense yellow color

 

Phenolphthalein

Color on the acidic side: colorless
Color on the basic side: pink
pH range of color change: 8.3-10.0
**meaning, the solution is colorless until it reach the pH of 8.3.

 

Now, imagine we have an acidic solution and water.

If we put drops of phenolphthalein in both solutions, the colors of both solutions will not change. It is because the pH of the acid and water is less than 8.3 and pH less than 8.3 will not have an intense pink color.

If we put drops of methyl orange in the acidic solution, the color of the solution will become red. But if we put drops of methyl orange in water, the solution will turn into yellow. It is because the pH of water, which is 7, is beyond the color range of methyl orange which is 4.4.

 

So the answer is Methyl orange.

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