A certain indicator, HA, has a Ka value of 1.3 × 10-6. The protonated form of the indicator is blue and the ionized form is red.

What is the pKa of the indicator?

What is the color of this indicator in a solution with pH = 8? Blue, red, or purple?

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  1. pKa=-log(Ka)=-log( 1.3 × 10-6)

    pH=pKa=log(A-/HA) solve for the ratio

    purple means ratio is one or very close to it

    blue means ratio is 1>

    red means ratio is 1<

    ****But check my thinking.

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