Which is true about scientific theories? (2 points)

They are proposed by scientists who wish to investigate a new topic.

They are the result of a single experiment.

They are only based on the most recent evidence.

They are the results of many experiments over a long period of time.

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.

Which sample at stp has the same number of atoms as 18 liters of ne at stp

Rank the four gases (air, exhaled air, gas produced from from decomposition of h2o2, gas from decomposition of nahco3) in order of increasing concentration of co2