pH and pKa
Comparing the pH to the pKa tells you which form of a species dominates. When pH < pKa, the protonated (acid, HA) form predominates; when pH > pKa, the deprotonated (conjugate base, A⁻) form predominates; at pH = pKa, the two forms are equal. Indicators change color by this same shift between forms.
The trap misunderstands indicator behavior — an indicator is a weak acid whose two forms (different colors) predominate on either side of its pKa, so its color change signals where the pH sits relative to that pKa.
The work
3 ways in · any order
Lesson
pH and pKa
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pH versus pKa decides the predominant form, and indicators work the same way. The lesson reads the predominant form and indicator behavior, then closes with a ten-scenario check.
Diagnostic
10-item topic check
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Ten items spanning the Topic 8.7 misconception: indicator behavior misunderstood — how the color-changing forms relate to pH and pKa.
Targeted Practice
Drill a single misconception
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Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.