Methyl orange is an indicator with a K_a of 1 * 10^-⁴. Its acid form, HIn, is red, while its base form, In^-, is yellow. At pH 6.0, the indicator will be

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At pH 6.0, the pH is much higher than the pKa of methyl orange (pKa = 4), meaning the solution is basic relative to the pKa. Therefore, the indicator will be in its base form, which is yellow.

Methyl Orange Is an Indicator with a Ka of 1

Methyl Orange Is an Indicator with a K_a of 1