the ionization constant, Ka, for and indicator, HIn, is 1.0x10^-8. The color of the unionized form is red and the color of the ionized form is yellow. What is the color of the indicator in a solution whose pH is 4.6? (Hint: the color of an indicator can be estimated by considering the ratio of [HIn]/[In]. If the ratio is equal to or greater than 10, the color will bet hat of the unionized form. If the ratio is equal to or smaller than 0.1, the color will be that of the ionized form.

Question

the ionization constant, Ka, for and indicator, HIn, is 1.0x10^-8.  The color of the unionized form is red and the color of the ionized form is yellow.  What is the color of the indicator in a solution whose pH is 4.6? (Hint: the color of an indicator can be estimated by considering the ratio of [HIn]/[In].  If the ratio is equal to or greater than 10, the color will bet hat of the unionized form.  If the ratio is equal to or smaller than 0.1, the color will be that of the ionized form.

aaronq · Answer

$HIn \rightleftharpoons H^+ +In^-$
write an equilibrium expression, substitute pH value in,  find the values of $In^-$ and $HIn$ and use the hint.