Copper metal can be recovered by burning copper (II) sulfide (Cus) in oxygen according to the reaction below:

CuS(s) + O2(g) → Cu(q) + SO2(g)

If this process is 81.1 % efficient
what mass (in kilograms) of copper will be made when 296.1 kilograms of copper (II) sulfide are reacted?

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.