A certain indicator HIn has a pKa of 9.00 and a color change becomes visible when 7.00% of it is In-.?

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A certain indicator HIn has a pKa of 9.00 and a color change becomes visible when 7.00% of it is In-.?

At what pH is this color change visible?
A. 7.88
B. 3.85
C. 10.2
D. 6.15
E. none of these

please provide explanation

2007-02-24 02:07:35 · 2 answers · asked by galdon885 1 in Science & Mathematics ➔ Chemistry

2 answers

Treat it like a buffer system and use the Henderson-Hasselbach equation.

You practically need to find the pH when 7% is in the In- form. Thus 93% will be in the HIn and if the total concentration of indicator is C, then [In-]=0.07C and [HIn]=0.93C

pH= pKa+log[In-]/[HIn] =
= 9.00 +log (0.07C/0.93C) =
=9+ log(7/93) =
=7.88

so the answer is A

2007-02-24 02:29:41 · answer #1 · answered by bellerophon 6 · 1⤊ 0⤋

Hin Indicator

2017-03-02 13:30:48 · answer #2 · answered by nussbaum 4 · 0⤊ 0⤋