Answer to Question #89169 in General Chemistry for Lim yoona

Question

An indicator can exist in two forms, depending on pH. One form is green, the other blue.

At pH 1, the indicator is entirely in the acid form (green). The absorbance of a 0.01 mol L-1 solution at 650 nm is 0.451.

At pH 10, the indicator is entirely in the base form (blue). The absorbance of a 0.01 mol L-1 solution at 650 nm is 0.131.

At pH 7, the absorbance of a 0.01 mol L-1 solution is 0.362. What percentage of the indicator is in the acid (green) form?

Answer 1

At pH 7, the absorbance of a 0.01 mol L-1 solution is 0.362,the percentage of the indicator is in the acid (green) form equal 50 % because at pH 7-neutral environment: $\lbrack$ H⁺$\rbrack$ =$\lbrack$ OH^-$\rbrack$ .