What does the entropy of a reaction describe? A. The amount of randomnes in the system
B. The amount of usable energy in a reaction
C. The number of molecules in a system
D. The amount of heat present in the system

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 of the following is a physical change? a.burning a piece of wood b.sawing a piece of wood in half c.rust forming on an iron fence d.a copper roof changing color from orange to green

Why are enzymes important to cells? they bring about chemical reactions. they provide structural support. they form the two layers of membranes. they store large quantities of energy.