One way to determine the pH of a solution is to measure the concentration of the...

One way to determine the pH of a solution is to measure the concentration of the acid and base forms of the indicator colorimetrically. In a solution where bromocresol green (pKa = 4.66) is used as the indicator, what is the pH of the solution when the concentration ratio of the acid to base form of the indicator is 1.75.

Expert Solution

The acid base reaction given by an indicator is

HIn + H2O ---> H3O+ + In-

Here the acid is HIn and the base is In-.

Given [HIn] / [In-] = 1.75

=> [In-] / [HIn] = 1/1.75 = 0.5714

Now pH of the solution can be calculated from Hendersen equation.

pH = pKa + log([In-] / [HIn]) = 4.66 + log0.5714 = 4.42 (answer)

queen_honey_blossom answered 2 years ago

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