A particular indicator has two forms-HIn in blue and In is yellow, and it has a
ID: 479787 • Letter: A
Question
A particular indicator has two forms-HIn in blue and In is yellow, and it has a pKa of 9.4. A different indicator has a pKa of 4.5, and the HIn form is red and the In- form is yellow. Two separate samples of a solution arc each tested with a different indicator. Interpret the following: (a) the first indicator is blue and the second indicator is red (b) the first indicator is blue and the second indicator is yellow (c) the first indicator is green and the second indicator is yellow (d) the first indicator is yellow and the second indicator is yellowExplanation / Answer
1. Indicator
(a) with first inidicator showing blue and second showing red : solution is acidic
(b) first is blue, second is yellow : the solution pH is above 4.5 but below 9.4
(c) first indicator is green and second indicator is yellow : the pH of solution is about 7
(d) the first indicator is yellow and second is yellow : pH of solution is above 9.4