When taking pH measurements of solutions, why is it important to stir thoroughly after adding each reagent? a. Mixing helps keep the solution components from contaminating the pH meter. b. A pH meter can only measure ions that are flowing past the meter at a fast speed. c. Mixing helps prevent precipitation of insoluble salts out of solution. d. Mixing helps ensure that the heasured pH is reflective of the entire solution.

The name of the ion, s2-, is: sulfurous ion sulfide ion sulfur ion sulfate ion

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.

Ab c or d ? i’m not sure what the answer is