A sample of silicon rejected for use in an electronic circuit has an impurity of boron at a level of 3 parts per trillion. What is the fraction of boron atoms in the silicon sample as written in scientific notation? In equation form 3 parts per trillion is written as 3/10^12 A) 3 x 10-12 B) 3 x 106 C) 3×10-9 D) 3 x 109

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.