Precipitation, Complexation, Redox Titration

Question

Five drops of dichlorofluorescein have been added to a solution containing a 0.800 g sample which required 25.30 mL of 0.100 M AgNO3.

(a) Identify the type of argentometric titration method used.

(b) Identify the indicator and endpoint color.

(c) Calculate the weight percent NaCl in the original sample.

Answer 1

(a) Based on the information provided, it appears that an argentometric titration method was used. Argentometric titrations involve the use of a solution of silver ions (Ag+) as the titrant, and are commonly used to determine the concentration of chloride ions (Cl-) in a solution.

(b) The indicator used in this titration is dichlorofluorescein. The endpoint color of the titration will depend on the concentration of Ag+ ions in the solution and the pH of the solution. At low concentrations of Ag+ ions and low pH, the solution will be yellow. As the concentration of Ag+ ions increases, the solution will turn orange, and at high concentrations of Ag+ ions and high pH, the solution will be pink.

(c) To calculate the weight percent NaCl in the original sample, we need to first determine the mass of NaCl present in the sample. This can be done using the following formula:

mass NaCl = (moles AgNO3 used) * (moles Cl- per mole AgNO3) * (molecular weight NaCl)

We can then divide the mass of NaCl by the total mass of the sample and multiply by 100% to express the result as a weight percent.