Answer to Question #102351 in General Chemistry for Amina

Question

A solution causes a yellow color with thymol blue, an orange color with methyl orange, a red color with methyl red, and a yellow color with bromthymol blue. The pH must lie between ________ and _______. The estimated pH is _______ +/- _______.

Answer 1

Depending on the pH, the color of solutions of thymol blue varies: in alkaline medium it is blue, in neutral it is yellow, in acidic it is raspberry red. pH dots color transition: from red to yellow 1.2-2.8, from yellow to blue 8.0-9.6.

The transition of the coloration of methyl orange in aqueous solutions from red to yellow is observed in the pH range 3.1-4.4 (in the acidic medium red, in alkaline - yellow.

The transition of the color of methyl red from red to yellow occurs at pH = 4.4-6.2.

Bromothymol blue registers changes in pH in the range from 5.8 to 7.6, changing its color from yellow to blue through shades of green.

The color of any indicator does not change with any change of pH, but only in the middle of a certain interval of pH, which is called the interval of transition of the indicator. For each indicator we take the mean value of the transition interval and calculate the approximate pH of the solution.

pH = (5.4 + 3.8 + 5.3 + 6.7) / 4

The estimated pH is 5.3 ± 1.5 .