alleryStart learning →Over what pH range does methyl orange complete its colour change?
AFrom 1.1 up to 2.4 on the pH scale
BFrom 4.4 up to 6.1 on the pH scale
CFrom 8.3 up to 10.0 on the pH scale
DFrom 3.1 up to 4.4 on the pH scale
Answer & Solution
Correct answer: D. From 3.1 up to 4.4 on the pH scale
1. Methyl orange is a weak acid whose two forms differ in colour.
2. Its undissociated form is red and its anion is yellow.
3. At a hydronium concentration of 8 x 10^-4 M, a pH of 3.1, the solution appears red.
4. At 4 x 10^-5 M, a pH of 4.4, most of the indicator is in the yellow form.
5. So the colour change interval runs from pH 3.1 to pH 4.4.
6. Beyond those limits further change in pH produces no visible difference.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 14 "Acid-Base Equilibria", section 14.7 Acid-Base Titrations_
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