Question

The indicator methyl red has a pKhln=4.95 . It changes from red to yellow over the pH range from 4.4 to 6.2.

If the indicator is placed in a buffer solution of Ph = 4.56, what percent of the indicator will be present in the acid form,Hln- , AND what percent will be present in the base or anion form, ln-?

If someone could please help me out, thanks in advance!!

Answer 1

I would use the Henderson-Hasselbalch equation.
4.56 = 4.95 + log (base)/(acid)
Solve for (B/A) ratio. Then
A + B = 100 (100 is just a convenient number)
Two equations in two unknowns. Solve for A and B and these will be in percent since we chose 100 as the total number of A+B.