Amal performs an experiment where he mixes hydrochloric acid and zinc metal together. He writes a chemical equation that he thinks models his experiment. 2HCl(aq)+Zn(s)→ZnCl2(aq)+H2(g)
Which evidence statement from the model suggests that a chemical reaction took place?

A
A gas was formed.

B
The color changed.

C
Heat was absorbed.

D
A precipitate formed.

Calculate the molarity of 48.0 ml of 6.00 m h2so4 diluted to 0.250 l .

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.

The organism shown is a free-living one that is anchored to the bottom of ponds and streams during one stage of its life cycle what is the common name for the group to which this organism belong