Bromthymol blue, an indicator with a Ka value of 1.00× 10-7, is yellow in its prorogated form and turns blue when protons are lost. For most indicators, about a tenth of the initial form must be converted to the other form before a new color is apparent. A few drops of this indicator is added to a strongly acidic solution which is then titrated with NaOH. At what pH will the indicator color change first be visible?