A mineral sample is analyzed for its cobalt and calcium content. A sample is dissolved, and then the cobalt and calcium are precipitated as Co ( OH ) 2 ( s ) and Ca ( OH ) 2 ( s ) . At what pH can Co ( OH ) 2 ( s ) be separated from Ca ( OH ) 2 ( s ) at 25 °C? Assume that an effective separation requires a maximum concentration of the less soluble hydroxide of 1 × 10 − 6 M .