Which of the following are true regarding ores?

I. Ores can be metallic.
II. Ores can be nonmetallic.
III. Ores consist of minerals.
IV. Materials removed from ores are useful.
A.
I, III, and IV only
B.
II, III, and IV only
C.
I, II, and III only
D.
I, II, III, and IV

A3.37-mg sample of protein was chemically digested to convert its nitrogen into ammonia and then diluted to 100.0 ml. then 10.0 ml of this solution was placed in a 50-ml volumetric flask and treated with 5 ml of phenol solution plus 2 ml of sodium hypochlorite solution. the sample was diluted to 50.0 ml, and the absorbance at 625 nm was measured in a 1.00-cm cuvette and found to be 0.486. for reference, a standard solution was prepared from 10.0 mg of nh4cl (molar mass = 53.49 grams/mole) dissolved in 1.00 l of water. then 10.0 ml of this standard was placed in a 50-ml volumetric flask, treated in the same manner as the unknown, and the absorbance found to be 0.323. finally, a reagent blank was prepared using distilled water in place of unknown, it was treated in the same manner as the unknown, and the absorbance found to be 0.076. calculate the weight percent of nitrogen in the protein.

Why does his teacher ask him to balance the equation by including the correct coefficient

The tendency of water molecules to stick together is referred to as a) adhesion b) polarity c) cohesion d) transpiration e) evaporation