Reacting (2R)−2−pentanol with HBr leads to the formation of equal amounts of (2R)−2−bromopentane and (2S)−2−bromopentane. Draw a stepwise mechanism for the reaction that is consistent with this observation.

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.